Fish with a musical tail (4)
I believe the answer is:
coda
'musical tail' is the definition.
(I've seen this in another clue)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for coda that I've seen before include "Final passage" , "Ending of musical piece" , "Closing part of a musical composition" , "Concluding section" , "finale in Beethoven?" .)