Sponsor and brief come together (5)
I believe the answer is:
angel
'sponsor' is the definition.
(angel is a kind of sponsor)
'and brief come together' is the wordplay.
'brief' means to remove the last letter (a shorter or briefer version of the word).
'come together' becomes 'gel' (gel can mean to go together well).
'and' with its last letter taken off is 'an'.
'an'+'gel'='ANGEL'
(Other definitions for angel that I've seen before include "Messenger of God" , "Investor in a theatrical production" , "Theatre backer" , "Guardian spirit; theatre investor" , "Cloud resident?" .)