Secret hero, roughly sixty (10)

I believe the answer is:

threescore

'sixty' is the definition.
(synonyms)

'secret hero roughly' is the wordplay.
'roughly' indicates an anagram.
'secret'+'hero'='secrethero'
'secrethero' is an anagram of 'THREESCORE'.

(Another definition for threescore that I've seen is " Sixty".)

I've seen this clue in The Guardian.

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