Extremely cruel act (8)
I believe the answer is:
atrocity
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">extremely cruel act</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for atrocity that I've seen before include "Barbarity, inhumanity" , "Evil act" , "Barbarous, inhuman act" , "Heinous deed" , "monstrous crime" .)