Related Clues:

• Nervous reaction
• One X of XXX
• Half a breath mint?
• See 6 Across
• Middle of three in a row?
• Middle of XXX or OOO
• -- -tac-toe
• Middle of a game
• Game name start
• Middle O, in a game
• Sign of nerves, perhaps
• Little jerk?
• One of three in a row
• Middle of three X's
• Game center