Possible Clues:

• 'Add led for what's laid long since (3,3)'
• Rotter has nasty urge
• Commanded the horse to get addled
• Won't sink down to the depths with local scoundrel
• Is capable of floating in water and that's presumably a problem for the layer
• Troublemaker is not up to scratch on English horse
• A rotten ovoid
• Malefactor
• Unsavory sort
• Type who's always causing trouble