Related Clues:

• Pitiable fool
• Jenny or jack
• Symbol of inflexibility
• Clot
• Utter doofus
• Palm Sunday transportation
• Dim bulb
• Low-emission transport?
• Pack bearer
• Beast that bore Balaam
• Horse's wild cousin
• Subject of many a 59-Down photo
• Butt of many a joke
• Onager, e.g.
• One may be kicked for motivation