Drink party not entirely dry (7)
I believe the answer is:
campari
'drink' is the definition.
(I've seen this before)
'party not entirely dry' is the wordplay.
'party' becomes 'camp' (both can mean a group of people).
'not entirely' means to remove the last letter (not all of the word).
'dry' becomes 'arid' (similar in meaning).
'arid' with its final letter removed is 'ari'.
'camp'+'ari'='CAMPARI'
(Other definitions for campari that I've seen before include "Pinkish aperitif" , "bitter drink" , "Red, bitter-sweet Italian aperitif" , "Mildly bitter aperitif, often drunk with soda" .)