The most common and most likely answer to this crossword clue is the 9 letter word MNEMONICS
I've seen this crossword clue in Independent
M
N
E
M
O
N
I
C
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 MNEMONICS mean?
MNEMONICS noun- Anything (especially something in verbal form) used to help remember something.
- The textual, human-readable form of an assembly language instruction, not including operands.
- The study of techniques for remembering anything more easily.