Related Clues:

• Perhaps it's ice that may have one furred up
• 15 across?
• You get it with lime and ice
• Might 23 down make fur?
• Some ice, perhaps, if there's lime in it
• H to O that's difficult, it seems
• Cause of limescale
• Cause of mineral buildup in faucets
• Pipe clogger, at times