Newly put on airer, uniform has shrunk (5)

I believe the answer is:

rerun

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'newly put' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.

'airer uniform has shrunk' is the wordplay.
'RERUN' is hidden within the letters.
But, I'm unsure how this is indicated.

'on' is the link.

Can you help me to learn more?

(Other definitions for rerun that I've seen before include "Show again on TV" , "Programme shown again" , "Repeat performance" , "Show (eg, film) again" , "rush again" .)

I've seen this clue in The Times.

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