The most common and most likely answer to this crossword clue is the 5 plus 4 letter word KNOCK DOWN
I've seen this crossword clue in Financial Times
K
N
O
C
K
D
O
W
N
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.