Beer's mine with an indefinite number consumed (4)
I believe the answer is:
pint
'beer's' is the definition.
'mine with an indefinite number consumed' is the wordplay.
'mine' becomes 'pt' (I can't explain this - if you can you should believe this answer much more).
'with' indicates putting letters inside.
'an' becomes 'i' (Roman numeral for one).
'indefinite number' becomes 'n' (mathematical symbol).
'consumed' means one lot of letters goes inside another.
'pt' going around 'i' is 'pit'.
'pit' going around 'n' is 'PINT'.
(Other definitions for pint that I've seen before include "Liquid meassure - four gills" , "Unit of beer" , "Quantity" , "small amount" , "Measure of the plain man's alcoholic drink" .)