Possible Clues:

• Mastery evokes one and a third cheers - stick around
• One working in lobby with assistance gets the advantage
• Party official meets Leader of House with advantage
• Wife kept secret about quiet with an advantage
• Dominating position
• Pinch collection from dealer in powerful position
• The control of the stock-holder?
• Advantage
• Position of power
• Controlling position (held by jockey?)