Has no one a right to this nickname? (5)

I believe the answer is:

lefty

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'has no one a right to this nickname?' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

This is the entire clue.

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(Other definitions for lefty that I've seen before include "Radical" , "Trot" , "Socialist; communist" .)

I've seen this clue in the Evening Standard.

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