Type of wine in claret's in abundance (7)
I believe the answer is:
retsina
'type of wine' is the definition.
(I know that Retsina is a type of wine)
'in claret's in abundance' is the wordplay.
'in' indicates the answer is hidden within the clue.
'RETSINA' is hidden within 'clarets in abundance'.
(Other definitions for retsina that I've seen before include "Type of Greek wine" , "Flavoured Greek white wine - nastier brand" , "Nastier (anag) - Greek wine" , "Oily-tasting Greek white wine" , "Nastier (anag) - white (or rose) wine" .)