Adaptation of Dune left many without excitement (9)

I believe the answer is:

mundanely

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'without excitement' is the definition.
I can't judge whether this defines the answer.

'adaptation of dune left many' is the wordplay.
'adaptation of' indicates anagramming the letters.
'left' becomes 'L' (common abbreviation).
'dune'+'l'+'many'='dunelmany'
'dunelmany' anagrammed gives 'MUNDANELY'.

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