Possible Clues:

• Be on both sides of
• Sit with one leg on either side of
• Oddly satire and adult entertainment first for high jump
• Lumber covers frame on Tower Bridge
• Lie on both sides of
• One who's on the fence
• Celebrated instrument led off — it's what cellists do
• Go across step half missing on rickety ladder
• Put pins around seat covers tailor's edging
• Sit astride rider's seat holding both ends of tether