Related Clues:

• Part of a wheel
• Volcano feature
• Orb, in prose
• Cyclops' singleton
• Crater edge
• Watcher
• Rope loop
• Part of a needle
• Mr. Potato Head part
• Glass edge
• Spy satellite, metaphorically
• Edge of a cup
• It's sometimes winkin' or blinkin,' but doesn't nod
• It's held in an orbit
• It may be public or evil