Bouncer possibly for party (4)
I believe the answer is:
ball
This clue is a double definition.
'bouncer' is the first definition.
(something that bounces)
'for party' is the second definition.
(ball is a kind of party)
'possibly' is the link.
(Other definitions for ball that I've seen before include "Social function for dancing" , "Party" , "Sphere - dance" , "Perhaps a bouncer < 's clog" , "Old song: 'After the .... was over'" .)