Sound character hidden in moon-graph (9)

I believe the answer is:

phonogram

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'sound character' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps you can see an association between them that I can't see?

'hidden in moon-graph' is the wordplay.
'hidden in' is an anagram indicator.
'moon'+'graph'='moongraph'
'moongraph' anagrammed gives 'PHONOGRAM'.

Can you help me to learn more?

(Another definition for phonogram that I've seen is " Character representing a sound".)

I've seen this clue in the Sydney Morning Herald.

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