Sherry is no good to old animal (11)
I believe the answer is:
amontillado
'sherry' is the definition.
(amontillado is a kind of sherry)
'no good to old animal' is the wordplay.
'no good' indicates an anagram (no good can mean faulty or defective).
'to'+'old'+'animal'='tooldanimal'
'tooldanimal' with letters rearranged gives 'AMONTILLADO'.
'is' is the link.
(Other definitions for amontillado that I've seen before include "Drink" , "Medium-dry sherry" , "booze" , "Pale sherry" , "Here's sherry" .)