Whirling around, party in bar (5)
I believe the answer is:
lever
'bar' is the definition.
(lever is a kind of bar)
'whirling around party' is the wordplay.
'whirling around' says the letters should be written in reverse.
'party' becomes 'revel' (I've seen this before).
'revel' in reverse letter order is 'LEVER'.
'in' acts as a link.
(Other definitions for lever that I've seen before include "Crowbar" , "Heavy bar" , "Means of exerting force" , "Rigid bar pivoting about a fulcrum" , "Revel with prising tool" .)