Firm belief in record blemish? (10)

I believe the answer is:

conviction

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'firm belief' is the definition.
(I've seen this in another clue)

I can't explain the remainder of the clue.

(Other definitions for conviction that I've seen before include "that may lead to imprisonment?" , "Certainty" , "Firm belief" , "it follows proof of guilt" , "in being found guilty" .)

I've seen this clue in the Sydney Morning Herald.

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