Petitioned firm about quote (9)

I believe the answer is:

solicited

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'petitioned' is the definition.
The answer and definition can be both to do with communicating as well as being past participle verbs.
Perhaps they are linked in a way I don't understand?

'firm about quote' is the wordplay.
'firm' becomes 'solid' (synonyms).
'about' is an insertion indicator.
'quote' becomes 'cite' (synonyms).
'solid' going around 'cite' is 'SOLICITED'.

Can you help me to learn more?

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

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