Most of the month's brandy (4)
I believe the answer is:
marc
'brandy' is the definition.
(marc is a kind of brandy)
'most of the month's' is the wordplay.
'most of' means to remove the last letter.
'the month' becomes 'march' (March is an example).
'march' with its last letter taken away is 'MARC'.
(Other definitions for marc that I've seen before include "A brandy; --- Chagall, artist" , "Sort of brandy made from the remains of pressed grapes" , "Strong liquor" , "Brandy distilled from grape residue" , "Cram (anag.)" .)