Weariness produced by an outspoken nuisance (5)
I believe the answer is:
ennui
'weariness' is the definition.
(ennui is weariness or boredom)
'produced by an outspoken nuisance' is the wordplay.
'produced by' indicates the answer is hidden within the clue (the clue produces a copy of the answer).
'ENNUI' can be found hidden inside 'outspoken nuisance'.
(Other definitions for ennui that I've seen before include "boring" , "doldrums" , "World-weariness" , "French boredom and lassitude" , "What's tedious and instils such listlessness" .)