Bacchanalian bash (4)
I believe the answer is:
orgy
'bacchanalian bash' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for orgy that I've seen before include "wild spree" , "Gory (anag.)" , "overindulgence" , "Wild revel" , "Riotous revel" .)