Informer

имя существительное осведомитель, информатор, доносчик Например: to turn informer — стать доносчиком police informer — полицейский информатор Синоним(ы): squealer, talebearer, stool pigeon

Большой англо-русский словарь

Informer

noun 1. one that imparts knowledge or news 2. one that informs against another; specifically one who makes a practice especially for a financial reward of informing against others for violations of penal laws

Merriam-Webster's Collegiate Dictionary