Fish or fruit only (5,4)
I believe the answer is:
lemon sole
'fish' is the definition.
(lemon sole is a kind of fish)
'fruit only' is the wordplay.
'fruit' becomes 'lemon' (lemon is a kind of fruit).
'only' becomes 'sole' ('sole' can be a synonym of 'only'**).
'lemon'+'sole'='LEMON SOLE'
'or' is the link.
(Other definitions for lemon sole that I've seen before include "swimmer" , "Tasty plaice of citrus origin?" , "Edible flatfish" , "fish to eat" , "Another tasty flatfish like lone citrus fruit" .)