Most of a month’s brandy (4)
I believe the answer is:
marc
'brandy' is the definition.
(I know that marc is a type of brandy)
'most of a month's' is the wordplay.
'most of' means to remove the last letter.
'a month' becomes 'March' (March is an example).
'march' with its final letter taken away is 'MARC'.
(Other definitions for marc that I've seen before include "Brandy made from fruit-refuse" , "Refuse from grapes after pressing - kind of brandy" , "Brandy distilled from grape residue" , "Fruit refuse" , "Drink" .)