Possible Clues:

• First of riders on horseback goes on to rouse his supporter?
• Foot support in riding
• Equestrian foothold
• You may put your foot in it
• Support for a rider�s foot
• Put your foot in it if you mix it up, perhaps
• Around start of race, instigate support for rider?
• Instigate right injection inside bone
• This helps one to hear small rumble of satisfaction, and it's rising
• Foot rest for a rider