The post work years tire me, the rent's overwhelming (10)

I believe the answer is:

retirement

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'the post work years' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

'tire me the rent's overwhelming' is the wordplay.
'overwhelming' means one lot of letters goes inside another.
'tire'+'me'='tireme'
'tireme' put within 'rent' is 'RETIREMENT'.

Can you help me to learn more?

(Other definitions for retirement that I've seen before include "Withdrawal" , "Process of withdrawing" , "Time without any work being done" , "Going to bed? - I met renter (anag)" , "Period after finishing work" .)

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

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