Unrepeated brief success (5,2,3,3)

I believe the answer is:

flash in the pan

(Other definitions for flash in the pan that I've seen before include "Fine hash plant (anag) - short-lived success" , "briefly successful thing" , "Nine-days wonder" , "First and only success" , "Ephemeral success" .)

I've seen this clue in The Guardian.

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