Possible Clues:

• Middle X, in a game
• Tic- -- -toe board
• The Northwest's Sea-__ Airport
• Tic ___ (mint)
• Part of XXX or OOO
• Toe preceder?
• Tic --
• 'Tic ___ Dough' (TV game show)
• Second of three X's
• Center of a marked success?