Brazen nuisances can display boredom (5)
I believe the answer is:
ennui
'boredom' is the definition.
(I know that boredom can be written as ennui)
'brazen nuisances can display' is the wordplay.
'display' indicates a hidden word (I've seen 'displayed' mean this (the answer is displayed within the clue)).
'ENNUI' is hidden within 'brazen nuisances can'.
(Other definitions for ennui that I've seen before include "Boredom in France" , "Mental weariness" , "Weariness with life" , "Lack of interest" , "Boredom, listlessness" .)