Got old two rethinking admission (4,4)

I believe the answer is:

wore thin

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'got old' is the definition.
Although both the answer and definition are past participle verbs, I don't see how one could define the other.

'two rethinking admission' is the wordplay.
'WORE THIN' is hidden in amongst the letters.
But, I am not sure how this is indicated.

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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