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