Impostor not quiet, left on top becomes a flop (5)

I believe the answer is:

loser

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'a flop' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for loser that I've seen before include "A failure, also-ran" , "One frequently failing" , "Unsuccessful competitor" , "Opposite of winner" , "Defeated person" .)

I've seen this clue in The Hindu.

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