Air beyond the clouds (5)
I believe the answer is:
ether
'air beyond the clouds' is the definition.
(I've seen this in another clue)
This is the entire clue.
(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" .)