Related Clues:

• Beast of burden
• Burro, for one
• Burro with a burden
• Mule or burro
• Mule or llama, e.g.
• Wild mink, alpaca and mule maybe
• Wolf, say, or a beast of burden
• Mixture of alpaca, mink, and llama, perhaps
• Llama in Peru, e.g
• Prospector's mule, e.g
• Mule, for example
• Yak or llama, e.g. (20-Across + 54-Across)
• Beast of burden, and a hint to 17-, 25-, 36- and 49-Across
• Perhaps llama or alpaca struggling with mink