I am quietly performing, exerting a noticeable effect (9)

I believe the answer is:

impacting

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'exerting a noticeable effect' is the definition.
I can't tell whether this definition defines the answer.

'i am quietly performing' is the wordplay.
'i am' becomes 'I'm' (contraction).
'quietly' becomes 'p' (p for piano and quiet).
'performing' becomes 'acting' (acting is a kind of performing).
'im'+'p'+'acting'='IMPACTING'

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(Another definition for impacting that I've seen is " striking".)

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

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