Nieces scorn ridiculous self-importance exhibited on stage (8)

I believe the answer is:

platform

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

I cannot understand how the remainder of the clue works.

(Other definitions for platform that I've seen before include "Stage for speaker or rail traveller" , "Raised stand" , "Raised dais" , "Raised horizontal surface" , "Party line" .)

I've seen this clue in The Irish Times.

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