Boredom featured by unseen nuisance (5)
I believe the answer is:
ennui
'boredom' is the definition.
(I know that boredom can be written as ennui)
'featured by unseen nuisance' is the wordplay.
'ENNUI' is hidden within the letters.
However, I am unsure how the hidden word is indicated.
Can you help me to learn more?
(Other definitions for ennui that I've seen before include "Boredom, dullness" , "French boredom and lassitude" , "Listless feeling" , "depression" , "to make one list less when connected" .)