Firebug's crime (5)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">firebug's crime</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for arson that I've seen before include "A burning crime" , "Felonious burning of property" , "Crime of fire setting" , "Iniquitous behaviour" , "Crime of fire raising" .)