Quart fraction (4)
I believe the answer is:
pint
'quart fraction' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pint that I've seen before include "Half a quart" , "Imperial measure of capacity" , "Glass of beer (colloq.)" , "Measure of the plain man's alcoholic drink" , "Standard measure of Guinness" .)