Lack of interest; boredom (5)
I believe the answer is:
ennui
I believe this is a double definition.
'lack of interest' is the first definition.
(I've seen this before)
'boredom' is the second definition.
(I know that boredom can be written as ennui)
(Other definitions for ennui that I've seen before include "Low interest rate" , "Bored listlessness" , "Weariness with life" , "Weary feeling" , "tiredness" .)