Doctor consuming end of bought fish (8)
I believe the answer is:
sturgeon
'fish' is the definition.
(sturgeon is a kind of fish)
'doctor consuming end of bought' is the wordplay.
'doctor' becomes 'surgeon' (surgeon is a kind of doctor).
'consuming' means one lot of letters goes inside another.
'end of' indicates one should take the final letters.
The final letter of 'bought' is 't'.
'surgeon' placed around 't' is 'STURGEON'.
(Other definitions for sturgeon that I've seen before include "The fish that yields caviar" , "Shark-like fish" , "Caviar supplier" , "Source of caviar" , "Fish producing caviar" .)