Related Clues:

• "Oh, shoot!"
• Cleaning challenge
• Disgusting buildup
• Disgusting stuff
• Old machinery coating
• Largely unrefined filth
• Dirt, say, swirling round edge
• It's nasty, brutish, short
• "Dang it!"
• Muck (slang)
• Grunge or gunk
• Golf crime drops Charlie in dirt
• Icky coating
• Mop target
• Scrubber's target