The most common and most likely answer to this crossword clue is the 2 plus 2 plus 7 letter word OF NO ACCOUNT
I've seen this crossword clue in The Daily Telegraph
O
F
N
O
A
C
C
O
U
N
T
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.