Related Clues:

• Odd habit
• A kind of twitch
• A little jerk?
• ''___ Tac Dough'' (game show)
• First 'O'?
• Fixation
• X or O, in a game
• Uncontrollable movement
• Habitual jerk
• Admitted the first customer
• Unlocked
• Made the first bet
• First of three O's, perhaps
• -- Tac (breath mint)
• Start of a grid game