The most common and most likely answer to this crossword clue is the 5 plus 7 plus 2 letter word DON’T MENTION IT
I've seen this crossword clue in Financial Times
D
O
N
â
€
™
T
M
E
N
T
I
O
N
I
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.