Related Clues:

• First of three O's, perhaps
• -- Tac (breath mint)
• Hiccup, for instance
• Start of a grid game
• Brief flash
• Habitual spasm
• Small spasmodic reaction
• Real jerk
• Quirky habit
• Muscle trouble
• Muscle cramp, e.g.
• Muscle jerk
• Nervous mannerism
• A real jerk
• Start of a grid-based game