Mark twenty (5)

I believe the answer is:

score

This clue is a double definition.

'mark' is the first definition.
('score' can be a synonym of 'mark')

'twenty' is the second definition.
('score' can be a synonym of 'twenty')

(Other definitions for score that I've seen before include "Points in a match" , "marks" , "Number of runs" , "Keep count" , "Reckoning" .)

I've seen this clue in The Times.

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