This clue initially tough? They weren’t troubled! (6-5)

I believe the answer is:

twenty-three

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

'initially tough? they weren't troubled' is the wordplay.
'initially' says to take the initial letters.
'troubled' is an anagram indicator.
The first letter of 'tough' is 't'.
'they'+'werent'='theywerent'
'theywerent' is an anagram of 'wentythree'.
't'+'wentythree'='TWENTY-THREE'

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I've seen this clue in The Times.

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