Related Clues:

• Derby, e.g.
• Mudder's day event
• Hustle
• Census datum
• Race
• 440 or 10K
• 100-meter, e.g.
• Hurtle
• 10K, e.g.
• Three-legged endeavor
• Olympic event
• Run quickly
• Breed
• See 65-Across
• See 18-Across