Wasted Moselle on fish (5,4)
I believe the answer is:
lemon sole
'fish' is the definition.
(lemon sole is a kind of fish)
'wasted moselle on' is the wordplay.
'wasted' indicates anagramming the letters.
'moselle'+'on'='moselleon'
'moselleon' with letters rearranged gives 'LEMON SOLE'.
(Other definitions for lemon sole that I've seen before include "swimmer" , "Another tasty flatfish like lone citrus fruit" , "Edible flatfish" , "Succulent flatfish associated with citrus fruit" , "Lose melon, find kind of plaice" .)