Related Clues:

• Causes to yawn, say
• Bad sorts to be stuck talking to at a gathering
• Periods of calm
• Doesn't interest
• Tidal floods? They are tedious
• Causes of much yawning
• They are tedious drills
• Drills; tedious people
• Drills black minerals
• Soothes to sleep
• Elicits yawns
• They might put you to sleep
• Tedious fellows