The most common and most likely answer to this crossword clue is the 12 letter word THOROUGHNESS
I've seen this crossword clue in The Sunday Telegraph
T
H
O
R
O
U
G
H
N
E
S
S
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 THOROUGHNESS mean?
THOROUGHNESS noun- The state of being thorough.
- Attention to detail.