Related Clues:

• Sudden contraction
• Sign of nerves
• Muscle contraction
• Three-legged calf, e.g.
• Involuntary twitch
• Recurrent twitch
• Antics
• An X could represent it
• Little jerk
• Peculiarity
• Three-legged calf, for one
• Involuntary muscular contraction
• Game opener?
• Marx Brothers antics, e.g.
• First X