Related Clues:

• Hollow cylinder
• Type of sock
• Eustachian, for one
• London transport
• Subway, to Brits
• River floater
• Cylindrical container
• Subway, in London
• Surfer's target
• TV channel
• Crest holder
• Part of CRT
• Bazooka part
• Test follower
• Toothpaste holder