Related Clues:

• Pester repeatedly
• Hassle
• Broken-down horse
• Annoying one
• Little brother, maybe
• Overworked horse
• Yapping dog, e.g.
• Stay on one's case
• D-Con target
• Bug bomb target
• Complain, complain, complain
• Hector
• Complain chronically
• Buttinsky, e.g.
• Spammer, for one