Lively party (4)
'lively party' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bash that I've seen before include "box" , "Social event - clobber" , "Hit hard; party (slang)" , "Batter" , "Dent - party" .)
'lively party' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for knees-up that I've seen before include "Lively informal party" , "Informal shindig (with Mother Brown?)" , "Riotous dance - party" , "Informal party with dancing" , "Lively party (colloq.)" .)