Illegal activity (5)
I believe the answer is:
crime
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">illegal activity</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for crime that I've seen before include "Felony" , "they say it doesn't pay" , "Illegal activity" , "A serious offence" , "Illegal act" .)