The most common and most likely answer to this crossword clue is the 9 letter word MEMORANDA
I've seen this crossword clue in Independent
M
E
M
O
R
A
N
D
A
More clues leading to the result MEMORANDA
- Notes male attorney’s written about return of capital
- Notes the writer meeting doctor at golf club
- Notes male attorney has penned backing City
- Mother is holding capital back together with notes
- Man-made or plastic notes
- Fellow touring ‘backward’ city with lawyer’s notes to self
- Norm made off before first of appointment reminders
- Man roamed all over the place making notes
- Notes man-made or manufactured
- Accepting Farah possibly raced, made rough notes
Buddy explains!

The straight part
We know that "notes to self" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case notes to self = memoranda.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 MEMORANDA mean?
MEMORANDA noun- A short note serving as a reminder.
- A written business communication.
- A brief diplomatic communication.
- A page in an annual publication honoring the memory of a person who died during the past year.