The most common and most likely answer to this crossword clue is the 9 letter word AFTERGLOW
I've seen this crossword clue in Financial Times
A
F
T
E
R
G
L
O
W
More clues leading to the result AFTERGLOW
- Swirling fog later with fading light
- Pleasant feelings in the matter of Government base
- German dons behind blue atmospheric phenomenon
- In which to bask where H comes down?
- Where you might find worms in skylight after sunset?
- Water golf rough in fading light
- Bursting, flow with great warm feeling
- Back down about amount of energy in fading light
- Fog later obscured west’s trace of sunset
- Nice feeling, possibly great, about initially feeling sad
Buddy explains!

The straight part
We know that "skylight after sunset" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case skylight after sunset = afterglow.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 AFTERGLOW mean?
AFTERGLOW noun- The glow seen in the sky after sunset.
- The light emitted by an incandescent object while cooling.
- The light emitted by a phosphor after excitation.
- The mildly euphoric feeling experienced after a pleasurable experience, especially after an orgasm or drug-induced high.
- An afterparty.