One covers NS&I fraud, standing firm (9)

I believe the answer is:

insisting

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

'one covers nsi fraud' is the wordplay.
'one' becomes 'i' (Roman numeral).
'covers' says to put letters next to each other.
'fraud' becomes 'sting' (sting is a kind of fraud).
'i'+'nsi'+'sting'='INSISTING'

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