Silently acting an operatic part is no good (6)

I believe the answer is:

miming

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'silently acting' is the definition.
'miming' can be an answer for 'acting' (thesaurus). I'm unsure of the 'silently' bit.

'operatic part is no good' is the wordplay.
'operatic part' becomes 'mimi' (I can't explain this - if you can you should believe this answer much more).
'is no good' becomes 'ng' (abbreviation).
'mimi'+'ng'='MIMING'

'an' acts as a link.

Can you help me to learn more?

(Other definitions for miming that I've seen before include "Pretending to sing" , "Acting without words" .)

I've seen this clue in the Evening Standard.

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