The most common and most likely answer to this crossword clue is the 12 letter word ALPHANUMERIC
I've seen this crossword clue in The Daily Telegraph
A
L
P
H
A
N
U
M
E
R
I
C
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 ALPHANUMERIC mean?
ALPHANUMERIC noun- An alphanumeric character.
- Consisting of, or limited to, letters and/or numbers, especially the characters A to Z (lowercase and uppercase) and 0 to 9.
- Consisting of these characters plus punctuation and other special characters.