Lad visited by doctor with answer -- avoid fish (6,4)
I believe the answer is:
bombay duck
'fish' is the definition.
(I've seen this before)
'lad visited by doctor with answer avoid' is the wordplay.
I cannot really see how this works, but
'doctor' could be 'mb' (Bachelor of Medicine, Medicinae Baccalaureus) and 'mb' is present in the answer.
'answer' could be 'a' (abbreviation eg in Q and A) and 'a' is found within the answer.
'lad' could be 'boy' (I've seen this in another clue) and 'boy' is found in the remaining letters.
'avoid' could be 'duck' (duck can mean to avoid) and 'duck' is found within the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for bombay duck that I've seen before include "one being caught in the deep?" , "Dried fish eaten with curry" , "Food" , "Dried curried fish" , "Dried fish dish" .)