Possible Clues:

• County nag has heavy burden
• Sign on, in foreign shores, a powerful beast
• Rent hotel or school in south-east Clydesdale, for one
• Animal father's taken round hospital — husky, say?
• Is he or she right about the heavy worker?
• Large draught animal
• Big nag should be quiet! - anger shown by husband, awfully sore
• One good at drawing sounds comparatively coy over drug
• Powerful breed of working animal