Possible Clues:

• If perhaps you mix this you'll put your foot in it
• Bone one puts the boot into
• Equestrian footrest
• Fuss over grabbing howler's tail bone
• The rest of the foot in the cavalry
• Put one's foot in it when up!
• Bone in the ear
• It helps to move higher round horse's middle
• Rider's foot loop
• Mix it, perhaps, and put your foot in it