Related Clues:

• Source of annoyance
• Tick, e.g.
• Incubus
• Little brother or spammer, to some
• Gnat or rat
• Enthusiast, plus
• Irksome fellow
• Starling, e.g.
• Slug, to a gardener
• Pain of a sort
• Possessor?
• Pain in the rear
• Mixed-up PETS?
• Exorcist's adversary
• Orkin victim