Interest in charity event (7)
I believe the answer is:
benefit
This clue is a double definition.
'interest' is the first definition.
(thesaurus)
'charity event' is the second definition.
(I've seen this before)
'in' acts as a link.
(Other definitions for benefit that I've seen before include "Charity event" , "(Gain) advantage" , "Fringe - -" , "Performance for charity" , "Fine bet (anag)" .)