Muses, say, why fishing might be unsuccessful? (5)

I believe the answer is:

nonet

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'muses say' is the definition.
The definition suggests a singular noun which matches the answer.

I can't explain the remainder of the clue.

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(Other definitions for nonet that I've seen before include "Band of nine?" , "Music for nine instruments or voices" , "Piece of music for nine" , "Piece for group" , "Piece for nine players" .)

I've seen this clue in The Times.

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