Atmospheric gas (5)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">atmospheric gas</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ozone that I've seen before include "Colourless gas, O3" , "Atmospheric layer in some danger" , "Sea-air" , "invigorating British air" , "Shield against radiation" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">atmospheric gas</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for oxygen that I've seen before include "A constituent of water" , "publicity, perhaps" , "Gas (of publicity?)" , "Twist together" , "Element essential to combustion" .)
(Other definitions for nitrogen that I've seen before include "Element - atomic no. 7" , "It's a gas, the strange ringtone" , "Main constituent of the air" , "Common gas, N" , "Much of what we take in" .)