Male boxer possibly making a comeback with different sponsor (9)
I believe the answer is:
godmother
'sponsor' is the definition.
(I know that godmother is a type of godparent)
'male boxer possibly making a comeback with different' is the wordplay.
'male' becomes 'm' (common abbreviation).
'boxer possibly' becomes 'dog' (boxer is a kind of dog).
'making a comeback' says the letters should be written in reverse.
'with' is a charade indicator (letters next to each other).
'different' becomes 'other' (similar in meaning).
'm'+'dog'='mdog'
'mdog' back-to-front is 'godm'.
'godm'+'other'='GODMOTHER'
(Other definitions for godmother that I've seen before include "sponsor" , "Stand-in for parent" , "Who's nominated" , "One in loco parentis" .)