Related Clues:

• ___ as a doornail
• Zebra relative
• Obstinate beast
• Aesop's thistle-eater
• One braying
• Horse's kin
• "... jawbone of an ___" (Judges 15:16)
• Working mammal
• Real jerk
• Very, very tired
• Metaphor for personal liability
• Like some phones or weights
• Sure-footed mammal
• Word with "duck" or "end"
• Sexual conquest