Possible Clues:

• That's a horse that's in for him for Ascot
• From a sheep you get a horse in his Scottish way
• A horse is the most of it, yet it's all from a sheep
• Traditional Scotch pudding
• Is there a sheep in it? His has a horse in it for Ascot, perhaps
• Scotish sheep dish
• Is there one horse in his sheepish mess?
• It seems that for a Scot there's a horse in his food
• Old crone one's taken round good Scottish food
• Burns's chieftain o' the puddin'-race