Witnesses experiment, one with funds (11)

I believe the answer is:

testimonies

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'witnesses' is the definition.
The definition and answer can be both related to communication as well as being plural nouns.
Maybe there's an association between them I don't understand?

'experiment one with funds' is the wordplay.
'experiment' becomes 'test' (test is a kind of experiment).
'one' becomes 'i' (Roman numeral).
'with' means one lot of letters go next to another.
'funds' becomes 'monies' (I've seen this in another clue).
'test'+'i'+'monies'='TESTIMONIES'

Can you help me to learn more?

I've seen this clue in The Times.

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