Possible Clues:

• Free-roaming horse
• Horse 'as to be strung up?
• Horse is obliged to hover round East End
• Idiot holding Laurel's horse
• Small feral horse of the US
• Obligation to turn nag into a horse?
• Wild animal gets Laurel in the face
• 'The horse fly,' you add, 'returned'
• Insect numbers on the rise, one running wild
• Problem affecting elephant, a no-good creature