The most common and most likely answer to this crossword clue is the 10 letter word MANUSCRIPT
I've seen this crossword clue in The Guardian
M
A
N
U
S
C
R
I
P
T
More clues leading to the result MANUSCRIPT
- Manchester United’s epitaph in court document
- Football team’s caught by trip arranged in writing
- Handwritten letter in old lady’s vault read out loud
- Handwriting being essentially lousy on instruction to pharmacist
- The earliest literary form
- Text seen in margins of memoirs?
- Ancient Indian writing — it can be sent to a publisher
Buddy explains!

The straight part
We know that "Handwritten" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case handwritten = manuscript.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 MANUSCRIPT mean?
MANUSCRIPT noun- A book, composition or any other document, written by hand (or manually typewritten), not mechanically reproduced.
- A single, original copy of a book, article, composition etc, written by hand or even printed, submitted as original for (copy-editing and) reproductive publication.
- Handwritten, or by extension manually typewritten, as opposed to being mechanically reproduced.