The most common and most likely answer to this crossword clue is the 12 letter word CONCATENATED
I've seen this crossword clue in The Guardian
C
O
N
C
A
T
E
N
A
T
E
D
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 CONCATENATED mean?
CONCATENATED verb- To join or link together, as though in a chain.
- To join (text strings) together.