One plucked posy in the end for rapacious monster (5)

I believe the answer is:

harpy

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'monster' is the definition.
(I know that Harpy is a type of mythical creature)

I can't explain the rest of the clue.

(Other definitions for harpy that I've seen before include "Nasty woman" , "Rapacious woman-bird" , "Ferocious woman" , "Ravenous monster -- nagging woman" , "Mythic bird with a woman's head" .)

I've seen this clue in The Guardian.

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