Related Clues:

• Cluster
• Wedlock, so to speak
• Speed unit
• Masseur's target
• Gut feeling?
• Shoelace problem
• Tough spot
• Shoelace woe
• Difficulty
• Hitch, e.g.
• Boy Scout's creation
• Nautical unit
• Muscle problem
• It's tied at the altar
• Bowline, for one