Historical clue formulations

• Informal informant — 2022-09-27
• Police informer — 2020-06-08
• Informer — 2019-08-04
• Police reporter? — 2015-03-27
• Singer in prison, maybe — 2015-02-24
• Sting participant — 2010-07-03
• One who sings but maybe shouldn't — 2006-02-17
• Ratfink — 2004-04-05
• Tell-all type — 2001-09-25
• Cop's contact — 1999-06-13
• Rat fink — 1998-10-05
• Informer — 1998-02-09
• Rat — 1997-04-24
• Informer, informally — 1994-10-02