The most common and most likely answer to this crossword clue is the 6 letter word CLUBBY
I've seen this crossword clue in The Daily Telegraph
C
L
U
B
B
Y
Buddy explains!

The straight part
We know that "sociable" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sociable = clubby.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 CLUBBY mean?
CLUBBY adjective- Resembling or suggestive of a social club or clubhouse: congenial and exclusive.
- Fond of frequenting nightclubs.