The most common and most likely answer to this crossword clue is the 9 letter word M-SIXTEEN
I've seen this crossword clue in Financial Times
M
-
S
I
X
T
E
E
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.