Party beat (6)
I believe the answer is:
thrash
This clue is a double definition.
'party' is the first definition.
(thrash can informally mean a party)
'beat' is the second definition.
(I know that thrash is a more specific form of beat)
(Other definitions for thrash that I've seen before include "stuff" , "Wallop" , "Drub" , "Beat thoroughly or make wild movements" , "Lay on - party" .)