The most common and most likely answer to this crossword clue is the 10 letter word COLLOQUIAL
I've seen this crossword clue in Financial Times
C
O
L
L
O
Q
U
I
A
L
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 COLLOQUIAL mean?
COLLOQUIAL noun- A colloquial word or phrase, colloquialism
- Denoting a manner of speaking or writing that is characteristic of familiar conversation, of common parlance; informal.
- Of or pertaining to a conversation; conversational or chatty.