There's only one winner (3)

I believe the answer is:

ace

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'winner' is the definition.

I don't understand how the rest of the clue works.

(Other definitions for ace that I've seen before include "Possibly a diamond" , "One or 11 in cards" , "Hole in one; very good" , "Service that's never returned" , "In golf, a hole in one" .)

I've seen this clue in the Evening Standard.

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