The most common and most likely answer to this crossword clue is the 9 letter word CELESTIAL
I've seen this crossword clue in The Guardian
C
E
L
E
S
T
I
A
L
More clues leading to the result CELESTIAL
- Divine lilac trees from which rook’s taken off
- Heavenly room accommodating one in fancy seat
- Heavenly performance of a cellist inspires ecstasy
- Divine tea is brewed in brother’s room
- Divine end to piece captured by a cellist in rhapsody
- Divine Satie composed in a small room
- Heavenly tea is prepared in small room
- Divine girl ensnares established lecturer
- Heavenly, Castile, rebuilt to enthral the Spanish
- Heavenly composition of Satie — little room to accommodate it
Buddy explains!

The straight part
We know that "Heavenly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case heavenly = celestial.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 CELESTIAL mean?
CELESTIAL noun- An inhabitant of heaven.
- Relating to the sky or outer space, regarded as the realm of the sun, moon, planets, and stars.
- Of or pertaining to the highest degree of glory.
- Of or pertaining to the heaven believed in by many religions.
- Of or pertaining to the kingdom of God; divine.
- Strongly or sublimely beautiful or pleasurable.
- (sometimes capitalized) A native of China.
- By extension, an East Asian person.