One who's able to improve your looks (7)

I believe the answer is:

oculist

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'one' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.

I can't explain the rest of the clue.

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(Other definitions for oculist that I've seen before include "Specialist in treatment of the eyes" , "Old-fashioned eye doctor" , "One working with seers" , "Optician" , "Treater of eyes" .)

I've seen this clue in The Irish Independent.

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