A setter is composing pieces of written work (9)

I believe the answer is:

treatises

I'm a little stuck... Click here to teach me more about this clue!

'pieces of written work' is the definition.
The definition and answer can be both related to communication as well as being plural nouns.
Perhaps you can see an association between them that I can't see?

'a setter is composing' is the wordplay.
'composing' indicates an anagram.
'a'+'setter'+'is'='asetteris'
'asetteris' is an anagram of 'TREATISES'.

Can you help me to learn more?

(Another definition for treatises that I've seen is " Formal pieces of writing".)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.