Amount of liquid consumed's endless, everyone being drunk (6)
I believe the answer is:
gallon
'amount of liquid' is the definition.
'consumed's endless everyone being drunk' is the wordplay.
'consumed' becomes 'gone'.
'endless' means to remove the last letter.
'everyone' becomes 'all' (I've seen this before).
'being drunk' means one lot of letters goes inside another (the inserted letters are consumed or drunk).
'gone' with its last letter removed is 'gon'.
'gon' enclosing 'all' is 'GALLON'.
(Other definitions for gallon that I've seen before include "Texans sometimes wear hats to hold ten of them" , "Unit of capacity" , "Unit equal to 4 quarts" , "Liquid measure" , "Imperial measure of capacity" .)