Related Clues:

• Threatened layer
• Imperiled layer
• __ layer
• A high flier may fly in it
• Eco-worry
• UV blocker
• Ultraviolet ray absorber
• Important type of layer
• Electrical storm byproduct
• Sensitive layer
• Ultraviolet radiation absorber
• Site of a worrisome hole
• Molecule also called trioxygen
• __ hole
• Layer up high