Bit of fish cooked for island (6,3)
I believe the answer is:
dorsal fin
'bit of fish' is the definition.
(I've seen this before)
'cooked for island' is the wordplay.
'cooked' is an anagram indicator (letters cooked into a new form).
'for'+'island'='forisland'
'forisland' with letters rearranged gives 'DORSAL FIN'.
(Other definitions for dorsal fin that I've seen before include "All that may be seen of shark" , "swimmer? Just a bit" , "Stabilising appendage on a fish's back" , "Projection on back of fish" , "bit of fish" .)