Related Clues:

• Gnat, often
• Bug you want to swat
• Source of exasperation
• Irritating sort
• Aphid, to a fruit tree
• Dennis the Menace, to Mr. Wilson
• Mosquito or mole, e.g.
• Fly, perhaps
• 17-Across in the neck
• Annoying bug
• Irksome one
• Pain in the ass
• One who 26-Across
• Destructive insect or nuisance
• A nuisance - step on it