Criminal underworld (8)
I believe the answer is:
gangland
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">criminal underworld</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 gangland that I've seen before include "World of organised crime" , "Criminal underworld" , "haunt of criminals?" , "Where to find mobsters" .)