Historical clue formulations

• With 86-Across, fixation problem suggested by this puzzle's theme — 2020-04-26
• Means of escaping prison, maybe — 2016-11-13
• Subway, basically — 2016-03-16
• Smuggling aid — 2014-09-20
• Ant farm feature — 2013-06-20
• Mole's work — 2012-03-11
• Path for a mole — 2010-03-08
• Prison escape route, maybe — 2004-03-16
• Dig — 2002-07-19
• Burrow — 1996-12-23