Related Clues:

• Response to a drone
• Night annoyance
• Nighttime annoyance
• Involuntary sign of tiredness or boredom
• Yawnfest
• [Bo-o-ring!]
• Uninteresting experience
• Make some z's
• A little night noise
• Take a sleep breath?
• Opening at an early-morning class?
• Embarrassing sound in a lecture hall
• Be open wide
• Bother for a bedfellow
• 'B-o-r-r-r-ing!'