The most common and most likely answer to this crossword clue is the 9 letter word KNEE-HIGH
I've seen this crossword clue in Financial Times
K
N
E
E
-
H
I
G
H
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 KNEE-HIGH mean?
KNEE-HIGH noun- (usually in the plural) A sock or stocking that reaches to the knees.
- Reaching to the height of a person's knees.