Arrangement of a duet with much diminuendo (4-3)

I believe the answer is:

fade-out

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'much diminuendo' is the definition.
The definition suggests a singular noun which matches the answer.

'arrangement of a duet' is the wordplay.
'arrangement' indicates anagramming the letters.
'of'+'a'+'duet'='ofaduet'
'ofaduet' is an anagram of 'FADE-OUT'.

'with' acts as a link.

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I've seen this clue in the Evening Standard.

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