Feeling of boredom (5)
I believe the answer is:
ennui
'feeling of boredom' is the definition.
(ennui is a feeling of boredom or discontent)
This is the entire clue.
(Other definitions for ennui that I've seen before include "French boredom and lassitude" , "Weary feeling" , "Lack of interest" , "Bored listlessness" , "Effect of boredom" .)