Crossword Genius

Like a score of ten from perfect substitute (6)

Ross

I believe the answer is:

double

This clue is a double definition.

'like a score of ten' is the first definition.
(score can mean twenty)

'perfect substitute' is the second definition.
(as in someone's double)

'from' acts as a link.

(Other definitions for double that I've seen before include "Designed for two users" , "Lookalike; twofold" , "Twice - bent over - run" , "Spitting image" , "Orwellian acceptance of conflicting principles" .)

I've seen this clue in The Times.
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