Boredom? Rotten nuisance? Not entirely (5)

I believe the answer is:

ennui

'boredom?' is the definition.
(I know that boredom can be written as ennui)

'rotten nuisance? not entirely' is the wordplay.
'not entirely' indicates the answer is hidden within the clue.
'ENNUI' is hidden within 'rotten nuisance'.

(Other definitions for ennui that I've seen before include "Listless feeling" , "Result of boredom" , "Bored listlessness" , "Feeling when tired of life?" , "Boredom or discontent" .)

I've seen this clue in The Times.

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