Dense forest (6)
I believe the answer is:
jungle
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">dense forest</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 jungle that I've seen before include "competitive environment" , "Deep tropical forest" , "Tangled vegetation" , "Dense tropical forest" , "Tropical rainforest area" .)