Historical clue formulations

• Liquid evidenced by the answers to this puzzle's starred clues? — 2019-03-20
• Means of secret writing ... or a description of a 17-Across? — 2009-05-15
• - — 2008-04-16
• First trick — 2005-05-17
• 34-Down for a stenographer? — 2003-03-31