Person with no faith in country where Democrat gains advancement (7)

I believe the answer is:

infidel

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'person' is the definition.
(infidel is a kind of person)

I don't understand the remainder of the clue.

(Other definitions for infidel that I've seen before include "One without religion (mainly archaic)" , "Heathen" , "Literally, 9 [UNFAITHFUL]" , "Person who rejects a religious belief" , "Sceptical" .)

I've seen this clue in The Times.

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