Drinking litres, bum virtually drunk (6)
I believe the answer is:
blotto
'drunk' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for blotto that I've seen before include "Blind drunk" , "Very drunk (informal)" , "Bombed" , "Drunken" , "Three sheets to the wind" .)