Feeling of listlessness (5)
I believe the answer is:
ennui
'feeling of listlessness' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for ennui that I've seen before include "Listless feeling" , "having nothing to do" , "Feeling when tired of life?" , "Mental weariness" , "Weariness with life" .)