Related Clues:

• Spying aircraft
• Tense drone across electric resistance with guitar beat
• Play lazily, as a guitar
• Go (on) dully
• Steady drone
• Hurdy-gurdy sound
• Surveillance tool
• Unmanned, unsettling military flier
• Finger-tapping sound
• No end to the peculiar beat
• Idle fellow, but he gives us a buzz
• Talk boringly; a parasite
• Talk boringly; male bee
• Bertie Wooster, say, is a boring speaker
• Strum; thread end