Fictional bear's an adherent of Hindu philosophical system (4)
I believe the answer is:
yogi
'fictional bear's' is the definition.
'yogi' can be an answer for 'bear's' (Cartoon character). I'm not sure about the 'fictional' bit.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for yogi that I've seen before include "Hindu mystic" , "Someone practising certain Hindu disciplines" , "Hindu spiritual ascetic" , "Cartoon bear (who has mastered Hindu philosophy?)" , "Hindu expert in spiritual discipline" .)