Parent, e.g.

• Parent, for example
• Nervous horse, perhaps
• Parent or guardian
• Terrified horse, at times
• Nanny, for one
• Parent or scared horse
• Skittish steed
• Frightened horse
• One bringing up children behind the Queen

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Rearer \Rear"er\ (r[=e]r"[~e]r), n. One who, or that which, rears.