Aggression (8)
I believe the answer is:
violence
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">aggression</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that violence is a type of aggression)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for violence that I've seen before include "The unlawful use of force, brutality" , "Destructive force" , "Acts of aggression" , "Harmful physical force" , "Force, injury" .)