Air beyond the clouds (5)
I believe the answer is:
ether
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">air beyond the clouds</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ether that I've seen before include "Imaginary interstellar medium" , "Medium supposedly" , "Anaesthetic liquid; clear sky" , "Type of chemical" , "Once widely-used anaesthetic" .)