Related Clues:

• When preceded by [the circled letters], natural shape said to be seen in 61-Across and 27-Down
• Curve, helix
• Staircase that winds round and round
• Like some space-saving staircases
• Corkscrew pasta's shape
• Well-tossed football
• Like the Vatican's Bramante Staircase
• Feature of a well-thrown football