Pyromaniac's crime (5)
I believe the answer is:
arson
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">pyromaniac's crime</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 arson that I've seen before include "Criminal activity" , "Malicious fire-raising" , "major crime" , "Crime of fire raising" , "Be pettish" .)