fink

nouns

someone acting as an informer or decoy for the police
canary, fink, sneak, sneaker, snitch, snitcher, stool pigeon, stoolie, stoolpigeon

verbs

take the place of work of someone on strike
blackleg, fink, rat, scab
confess to a punishable or reprehensible deed, usually under pressure
confess, fink, squeal