Party animal (4)
I believe the answer is:
stag
This clue is a double definition.
'party' is the first definition.
(stag party is a kind of party)
'animal' is the second definition.
(stag is a kind of animal)
(Other definitions for stag that I've seen before include "American party" , "Game - speculator" , "animal of the deer family" , "Unaccompanied man at party" , "Horned animal" .)