The most common and most likely answer to this crossword clue is the 9 letter word ROOTBOUND
I've seen this crossword clue in The Guardian
R
O
O
T
B
O
U
N
D
Buddy explains!
The straight part
We know that "Growth-restricted" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case growth-restricted = rootbound.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 ROOTBOUND mean?
ROOTBOUND adjective- (of a pot plant) Having outgrown its pot, so that the roots are cramped and tangled.