Possible Clues:

• Rules announced as means of control
• They control the kidneys
• Straps
• Straps to control
• Controlling interests?
• Sounds as if it's not so fine for the rider's siren
• Sounds as it it's wet enough to have them in hand
• Horse halters
• Trigger pullers?
• There are certain to be a lot of loose ones in the Grand National