Possible Clues:

• Put your foot in it when you're up
• Begin to mix it up in the end and put your foot in it
• Support
• Mix it up, by the sound of it, and you've put your foot in it
• This cup is taken up
• It's important to one's standing as a rider
• Metal loop on riding saddle
• In which a rider's foot rests
• Horseman might put his foot in it
• Small thing needed in hearing to get Republican excited