The most common and most likely answer to this crossword clue is the 5 letter word ETHER
I've seen this crossword clue in The Times
E
T
H
E
R
More clues leading to the result ETHER
- Anodyne article appears in Queen
- Raise the rate to screen Sky
- Article inspired by Her Majesty’s knockout drops?
- I'm volatile in that place, the first to rise up
- . Film husband turned over on Sky
- Film the woman’s gas
- Subtracting unspecified number from lower number
- Lacking information, one or the other might knock you out
- Air film with that woman
- Number of the chalet herewith
Buddy explains!

The straight part
We know that "Sky" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sky = ether.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ETHER mean?
ETHER noun- The substance formerly supposed to fill the upper regions of the atmosphere above the clouds, in particular as a medium breathed by deities.
- Often as aether and more fully as luminiferous aether: a substance once thought to fill all unoccupied space that allowed electromagnetic waves to pass through it and interact with matter, without exerting any resistance to matter or energy; its existence was disproved by the 1887 Michelson–Morley experiment and the theory of relativity propounded by Albert Einstein (1879–1955).
- The atmosphere or space as a medium for broadcasting radio and television signals; also, a notional space through which Internet and other digital communications take place; cyberspace.
- A particular quality created by or surrounding an object, person, or place; an atmosphere, an aura.
- Diethyl ether (C4H10O), an organic compound with a sweet odour used in the past as an anaesthetic.
- Any of a class of organic compounds containing an oxygen atom bonded to two hydrocarbon groups.
- To viciously humiliate or insult.