Possible Clues:

• Beast on a coat of arms
• Creature of myth
• Horned creature
• One on ahead for you, by the sound of it, grain of the North
• One brief problem afoot for wonder horse
• One might horn in from you with your crop north of the Border
• Mythical beast like horned horse
• Mythical white animal with long horn
• Fabulous beast like horned horse
• Fabulous supporter of royalty