Possible Clues:

• Become coated with a frozen layer
• Become blocked, in a way
• Cooler at height, so get coat
• Become impassable, in a way
• Become translucent, as a windshield
• Become frosted, as a windshield
• Need defrosting
• Get frosted, as glass
• Get more than frosty
• I see European Union political leader to get a winter coat perhaps