Drunk a lot on a mild sherry (11)
I believe the answer is:
amontillado
'sherry' is the definition.
(amontillado is a kind of sherry)
'drunk a lot on a mild' is the wordplay.
'drunk' indicates anagramming the letters.
'a'+'lot'+'on'+'a'+'mild'='alotonamild'
'alotonamild' with letters rearranged gives 'AMONTILLADO'.
(Other definitions for amontillado that I've seen before include "Drink" , "Pale sherry" , "Here's sherry" , "booze" , "Medium-dry sherry" .)