Related Clues:

• Part of a winning combination
• One-third of XXX?
• The first X of X-X-X
• See 13-Down
• Mannerism
• Certain X
• Behavioral quirk
• Quirk
• See 23-Across
• Middle of a kids' game
• Twitch
• Facial spasm
• See 24-Across
• Sign of nervousness
• See 53-Down