Related Clues:

• One's put on weight — it's something in the air
• Australia has a single chicken and it's fast disappearing
• Australia's a gas!
• That precious layer
• Bracing seaside air
• Gas (with a layer)
• Fresh, bracing sea air
• Sea air (found in layer?)
• Colourless gas
• Shield against radiation
• Allotrope of oxygen
• Less common form of oxygen
• Gas (in a layer?)
• Part of upper atmosphere giving protection from ultraviolet rays
• (Depleted) layer of gas