Related Clues:

• Frozen over
• Froze
• Became frozen
• Got slick
• Became frosted
• Needing defrosting
• Froze solid
• Became slick
• Needed a coating of heated propylene glycol, say
• Slick, in a way
• Got frosty
• Got frozen
• Became a winter hazard, as a road
• Covered in a sheet?
• Got slick after sleet