Related Clues:

• Old chestnut, maybe
• Worn-out mount
• Dun horse?
• Ride, in a way
• Past-its-prime horse
• Pester and pester
• Pester nonstop
• Bug repeatedly
• Equine badger!
• Horse giving worry
• Remind over and over again
• Bug persistently
• Harry to keep on complaining
• Bother and bother
• When said three times, 'Get off my case!'