Related Clues:

• Sound from a sleep lab
• Sleep disturbance
• Like school, sometimes
• Bother one's bedmate
• Make a little 'night music'
• See 94-Down
• See 18-Across
• See 43-Across
• Sack sound
• 'Zzzzzz ...'
• See 40-Down
• Word with falling or flat
• Not safe
• Ump's ruling
• Absent