Doctor has a boneless fish (7)
I believe the answer is:
surgeon
'doctor' is the definition.
(I know that doctor can be written as surgeon)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for surgeon that I've seen before include "One who operates" , "Medical knife wielder" , "Go, nurse for the operator" , "Physician" , "Theatre operator" .)