Crossword Genius

Earth's upper layer of protection (5)

Ross

I believe the answer is:

ozone

(Other definitions for ozone that I've seen before include "Allotrope of oxygen" , "Layer that protects against ultraviolet rays" , "Atmospheric gas shielding us from ultraviolet radiation" , "It's said to brace" , "something refreshing" .)

I've seen this clue in the Sydney Morning Herald.
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