Ruin drop of cherry brandy (4)
I believe the answer is:
marc
'brandy' is the definition.
(marc is a kind of brandy)
'ruin drop of cherry' is the wordplay.
'ruin' becomes 'mar' (I've seen this before).
'drop of' indicates taking the first letters.
The initial letter of 'cherry' is 'c'.
'mar'+'c'='MARC'
(Other definitions for marc that I've seen before include "Type of eau-de-vie made from residue of grapes" , "Cram (anag.)" , "Sort of brandy made from the remains of pressed grapes" , "Strong liquor" , "Brandy made from fruit-refuse" .)