Boredom when nuisances part (5)
I believe the answer is:
ennui
'boredom' is the definition.
(I know that boredom can be written as ennui)
'when nuisances part' is the wordplay.
'part' says the answer is hidden in the clue.
'ENNUI' is hidden within 'when nuisances'.
(Other definitions for ennui that I've seen before include "Boredom, dullness" , "World-weariness" , "French boredom and lassitude" , "Bored listlessness" , "Weary feeling" .)