Beautiful flier, outside left again (5)

I believe the answer is:

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'beautiful flier' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps there's an association between them I don't understand?

I cannot understand how the remainder of the clue works.

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(Other definitions for belle that I've seen before include "Attractive woman" , "Beautiful girl" , "Pretty girl" , "-- Epoque, before the Great War" , "Handsome lady of the Ball?" .)

I've seen this clue in the Evening Standard.

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