French composer’s communication on opening of rondeau (8)

I believe the answer is:

messager

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'french composer's' is the definition.
'messager' can be an answer for 'composer's' (I've seen this before). I am not sure about the 'french' bit.

'communication on opening of rondeau' is the wordplay.
'communication' becomes 'message' (a message is something communicated).
'on' says to put letters next to each other.
'opening of' indicates taking the first letters.
The first letter of 'rondeau' is 'r'.
'message'+'r'='MESSAGER'

Can you help me to learn more?

(Another definition for messager that I've seen is " COMPOSER".)

I've seen this clue in The Times.

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