Possible Clues:

• Towel specification
• Pulp "His 'n' ___"
• Wife's vanity plate pronoun, perhaps
• Word on one of a matching pair
• "If she did play false, the fault was __": Shak
• For a lady
• For the goose, not the gander?
• Peter Murphy "His Circle and ___ Meet"
• Word not in the Constitution, as Stanton noted
• Vanity plate in a two-car garage, perhaps