After training, Perth girl is more nimble (11)

I believe the answer is:

sprightlier

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'more nimble' is the definition.

'after training perth girl is' is the wordplay.
'perth girl is' can be anagrammed to 'SPRIGHTLIER'.
However, I'm not sure how this is indicated.

Can you help me to learn more?

I've seen this clue in The Everyman puzzle in The Observer.

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