Drunken bum getting cut, swallowing litre (6)
I believe the answer is:
blotto
'drunken' is the definition.
(slang term)
'bum getting cut swallowing litre' is the wordplay.
'bum' becomes 'bottom' (bum can informally mean one's bottom).
'getting cut' means to remove the last letter.
'swallowing' is an insertion indicator.
'litre' becomes 'L' (abbreviation).
'bottom' with its last letter taken off is 'botto'.
'botto' enclosing 'l' is 'BLOTTO'.
(Other definitions for blotto that I've seen before include "Stoned" , "Dead drunk" , "Boot Lt. out for being drunk" , "Wasted" , "Cockeyed drunk" .)