Sort of drink — celebrate, imbibing litre (5)
I believe the answer is:
sling
'sort of drink' is the definition.
'celebrate imbibing litre' is the wordplay.
'celebrate' becomes 'sing' (I've seen this before).
'imbibing' means one lot of letters goes inside another.
'litre' becomes 'l' ('l' can be a synonym of 'litre').
'sing' going around 'l' is 'SLING'.
(Other definitions for sling that I've seen before include "attached to a rifle, perhaps" , "Cast - used for injured arm" , "Stone-throwing weapon" , "throwing implement like catapult" , "Cloth to support arm" .)