As for your question about the alleged hadith, we should say that we looked for it in our hadith collections but we did not find it.
As for the definition of philosophy, it has been defined in a number of different ways, and in one of the definitions, philosophy has been defined as a discipline that discusses being (mawjud) qua being. Its subject deals with the essential properties of being qua being. Its end is to achieve a general knowledge of existents and to distinguish them from that which is not really existent. When it comes to the third part of your question, we must say that the term “bad” is not commonly used in regard to philosophy. In fact, there have been some people in the history of science who have opposed philosophy for some reasons. For instance, Al-Ghazzali has raised certain criticisms in his Tahāfut al-Falasifa (The Incoherence of the Philosophers) but Ibn Rushd (Averroes) has rejected all those criticisms in Tahāfut al- Tahāfut (The Incoherence of the Incoherence). Those who are opposed to philosophy maintain that the fundamentals and problems of philosophy stand in contrast with the religion whereas it is not the case. Great philosophers like Mulla Sadra have stated that philosophy does not contradict with religious teachings and principles. Therefore, not only we should not oppose philosophy but we should also endeavor to learn it well.
As for the first part of the question, we went through many hadith collections to find the hadith but we could not find it anywhere. It would have been better if you gave the reference for the said tradition so that we could conduct a research into it and give you a more precise answer.
When it comes to the second part of your question i.e. the definition of philosophy, we must say that philosophy has been defined in a number of different ways, and in one of the definitions, philosophy has been defined as a discipline that discusses being (mawjud) qua being. In fact, philosophy is the knowledge of the realities of things, as they are in fact, so that through knowing these realities and the objective order of the world, man may realize in himself a microcosmic rational order, which corresponds to the objective world.
When it comes to the third part of your question, we must say that the term “bad” is not commonly used in regard to philosophy. In fact, there have been some people in the history of science who have opposed philosophy. Different people have opposed philosophy with different motives. However, those of the learned, informed and unbiased scholars who have opposed philosophy, they have in reality opposed the common set of philosophical ideas some of which were not compatible with Islamic principles. Perhaps, if there is a valid narration censuring or reproofing philosophy, it is because of those incompatible ideas. When we speak of philosophy, we do not insist on all the philosophers’ views and statements being right. In fact, what we mean by philosophical attempt is the application of reason in understanding issues that can be resolved only through intellection. This endeavor has been recommended by Quranic verses as well as traditions; just like the arguments which have been produced in the Book and tradition concerning monotheism and resurrection.
Now it is necessary to go through the arguments presented by the opponents of philosophy:
One of the reasons for opposing philosophy is that if philosophy could solve any problems and had any benefit, then why do philosophers disagree on a subject? In other words, the best reason for them to reproof philosophy is the discrepancy existing among the philosophers themselves causing the scholars to lose their confidence in the validity of their methods. In response to these objections, the proponents of philosophy say that discrepancies exist in every science such as those existing in mathematics. For example, if two individuals have different opinions on a mathematical issue, we cannot judge that mathematics is useless and void. As a matter of fact, these differences can motivate the expert in that branch of knowledge to further their efforts until they can reach more reliable results.
Another reason for opposing philosophy is what the philosophers say is opposed to the religion. For example, al-Ghazzali is one of the opponents of philosophy. He has opposed philosophy in his book Tahāfut al-Falasifa (The Incoherence of the Philosophers) and has said that what philosophers are saying end up in many cases in kufr (infidelity). For example, the philosophical ideas relating to God’s knowledge, the eternity of the world and physical resurrection are opposed to religious beliefs. But Averroes (Ibn Rushd) wrote Tahāfut al-Tahāfut (The Incoherence of the Incoherence) in response to al-Ghazzali’s objections. He has rejected al-Ghazzali’s arguments at length. He says, “If there are some differences between the religion and philosophy, they are related to the philosophical allegations of those who claim to be theosophists and philosophers whereas they have understood nothing from philosophy. If there is anyone who is well acquainted with philosophy and method of intellection, he knows very well that philosophical ideas are in no way in contrast with religion.
Another reason to prove that real philosophers do not oppose the religion and religious principles is the saying of the greatest Islamic philosopher, Sadrul Muta’llehin (Mulla Sadra) who says in his book, the Four Journeys (al-Asfar al-Arba’ah):
تباً لفلسفة تكون قوانینها غیر مطابقة للكتاب و السنة
“Curse and death to any philosophy whose rules and principles are incompatible with the Book and tradition (Sunnah).” 
Not only have the proponents of philosophy answered the spurious arguments by the proponents but they have also explained the need for philosophy. For instance, they have said that basically true humanity depends on philosophical achievements in the sense that man’s privilege or distinction rests in his vision and tendency. Hence, if an individual suffices only to physical conceptions and does not use properly the faculty of reason, he cannot be a real human being. Philosophy consolidates the power of intellect or the faculty of reason in man.
Accordingly, a true human being is one who uses his intelligence in understanding the most important and most crucial issues to learn generally how to live a life. Basically, identifying and understanding issues that are crucial to man depend on philosophical attempts.
Having said that and in view of the evidence we provided, we can conclude that philosophy is not bad and there is no reason to oppose it.
 - See: Mesbah Yazdi, Muhammad Taqi, Philosophical Instructions, vol.1, Bainulmelal (International) Publications, 7th edition 1387 (2009).
 - Philosophical Instructions, vol.1, pg. 137.
 - Philosophical Instructions, vol.1, pg. 135.
 - Ghazzali, Muhammad, Tahafut al-Falasifa (The Incoherence of Philosophers), pg. 44, Beirut.
 - Ibn Rushd, Faslul Maqal, p.g 26 cited from Naqd-o- Nazar (Specialized philosophy journal), 11th year, No. 1 & 2, year 1385 (2006),pg. 181.
 - Mulla Sadra, Al-Arba’ah, vol.8, pg. 303, Dar al-Ma’aref al-Islamiyah, 1378 A.H. Tehran.
 - Philosophical Instructions, vol.1 pg. 135.