Related Clues:

• Space between the teeth, e.g.
• Cleft
• Obstacle in father-son relations
• Rift
• Canyon, e.g.
• Great joy
• Disconnection
• Unfilled space
• Dental problem calling for braces
• Inner space
• Cumberland, for one
• Nixon tape mystery
• Chain with threads?
• Feature of Alfred E. Neuman's smile
• David Letterman feature