The most common and most likely answer to this crossword clue is the 9 letter word LEAFINESS
I've seen this crossword clue in The Times
L
E
A
F
I
N
E
S
S
More clues leading to the result LEAFINESS
- Field expertise reduced amount of green growth
- Property of trees in meadows: healthy inside with sun
- Green character Alfie roamed headland
- Green state imposed penalty probing corrupt sales
- A feature of woodland, meadow and narrow borders of spinneys
- Being green, Elsa’s recycled bottles very well
- Punishes breaking into fields having much greenery
Buddy explains!
The straight part
We know that "amount of green growth" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case amount of green growth = leafiness.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.