Referee's informant? (7-6)

I believe the answer is:

whistle-blower

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(Other definitions for whistle-blower that I've seen before include "Teller of tales to the authorities - referee?" , "Informant on malpractice" , "Person revealing improper activities" , "One who exposes wrongdoing" , "Person with inside information making public some illicit activity" .)

I've seen this clue in The Times.

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