Party behind gifts (7)
I believe the answer is:
donates
'gifts' is the definition.
(donating is a kind of gifting)
'party behind' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'behind' becomes 'nates' (both can mean the buttocks).
'do'+'nates'='DONATES'
(Other definitions for donates that I've seen before include "Offers free" , "gifts" , "Gives to good cause" .)