Weak enough to flop outright (5)

I believe the answer is:

frail

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'weak' is the definition.
(I know that weak can be written as frail)

I don't understand the remainder of the clue.

(Other definitions for frail that I've seen before include "American woman" , "Physically feeble" , "isn't sturdy" , "Easily destroyed" , "Old woman" .)

I've seen this clue in the Evening Standard.

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