The most common and most likely answer to this crossword clue is the 9 letter word FLOWERING
I've seen this crossword clue in The Daily Telegraph
F
L
O
W
E
R
I
N
G
Buddy explains!

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 FLOWERING mean?
FLOWERING verb- To put forth blooms.
- To decorate with pictures of flowers.
- To reach a state of full development or achievement.
- To froth; to ferment gently, as new beer.
- To come off as flowers by sublimation.
- The action of the verb to flower.
- The period of time during which a plant is in flower.
- The period of time during which someone or something is at its peak.
- (used only before the noun) Of a plant, that produces flowers.
- Aflower, in bloom