Unhappiness (6)
I believe the answer is:
misery
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">unhappiness</span>' is the definition.<br/ ><span class="explanation-format__explanation">(misery is a kind of unhappiness)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for misery that I've seen before include "Despair" , "Party-pooper" , "Wretched state" , "Great distress or discomfort" , "Torment" .)