One litre left for everybody (3)
I believe the answer is:
all
'everybody' is the definition.
(all people)
'one litre left' is the wordplay.
'one' becomes 'a' (a thing is one thing).
'litre' becomes 'L' (abbreviation).
'left' becomes 'l' (common abbreviation).
'a'+'l'+'l'='ALL'
'for' acts as a link.
(Other definitions for all that I've seen before include "The whole quantity" , "Straight garden path" , "Monopolist controls this" , "Everyone - complete" , "in toto" .)