Related Clues:

• Quandary
• Slangy 'Au contraire!'
• Oft-contracted word
• Tough nut
• Tie tightly
• Headscratcher
• '___ so fast!'
• Nautical unit
• Negator's word
• Stumper
• Muscle problem
• Enigma
• It's tied at the altar
• Bowline, for one
• Gordian or slip follower