The most common and most likely answer to this crossword clue is the 12 letter word AIDE-MEMOIRE
A
I
D
E
-
M
E
M
O
I
R
E
More clues leading to the result AIDE-MEMOIRE
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 AIDE-MEMOIRE mean?
AIDE-MEMOIRE noun- A memory-aid; a reminder or memorandum, especially a book or document serving this purpose.
- A document circulated in a meeting or summit for discussion purposes (also termed a non-paper)