Youth leader will go back with a philosophy (4)
I believe the answer is:
yoga
'philosophy' is the definition.
(I know that yoga is a type of Indian philosophy)
'youth leader will go back with a' is the wordplay.
'youth leader' becomes 'y' (I've seen this in other clues).
'will' says to put letters next to each other (I've seen this in other clues).
'back' shows that the letters should be reversed in order.
'with' says to put letters next to each other.
'go' in reverse letter order is 'og'.
'y'+'og'+'a'='YOGA'
(Other definitions for yoga that I've seen before include "Hindu philosophy of tranquility through physical exercise" , "E.g. Lotus position" , "Hindu philosophy of tranquillity through physical exercise" , "Hindu spiritual and ascetic discipline" , "Hindu system of meditation and self-control" .)