The most common and most likely answer to this crossword clue is the 6 letter word NOTATE
I've seen this crossword clue in Financial Times
N
O
T
A
T
E
More clues leading to the result NOTATE
- Write a score part for one of the foregoing? Ta – terriffc
- Write symbolically a message including thanks
- Be a composer, not a vacuous Trumpite!
- Compose a short statement welcoming volunteers
- What music maker may do conducting at Eton
- There’s appreciation in college about what composer does?
- Write down some music? Not a note!
- Indicate how to play number to gallery
- Record in bars showing lack of an artistic patron?
- Write down impression about volunteers
Buddy explains!

The straight part
We know that "Write down" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case write down = notate.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 NOTATE mean?
NOTATE verb- To mark with spots or lines, which are often colored.
- To add notes to; to annotate
- To create notation (i.e. music); to record/put down in the form of notation
- Marked with coloured spots or lines.