Auditor's most appropriate passion for another auditor? (8)

I believe the answer is:

verifier

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'auditor?' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see a link between them that I can't see?

I can't explain the remainder of the clue.

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(Other definitions for verifier that I've seen before include "One confirming" , "One checking" .)

I've seen this clue in The Independent.

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