Wife aboard scooter turning forty (3-5)

I believe the answer is:

two-score

'forty' is the definition.
(a score means twenty)

'wife aboard scooter turning' is the wordplay.
'wife' becomes 'w' (abbreviation).
'aboard' means one lot of letters goes inside another.
'turning' is an anagram indicator.
'scooter' is an anagram of 'toscore'.
'w' placed within 'toscore' is 'TWO-SCORE'.

I've seen this clue in The Independent.

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