Possible Clues:

• Stumble at the start to a race?
• Urge turning in a celebrity causing shock
• How a horse might begin to fall among the rest
• Sounds more like a buck, perhaps, that may be about to fall
• More like a buck, perhaps, before the fall
• Reel about; shock
• To stumble, one buck gets Reginald up
• Surprise move by someone under the table?
• Cause to reel
• They label back to front to confound