Imposing entrance (6)
I believe the answer is:
portal
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">imposing entrance</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 portal that I've seen before include "An imposing gateway" , "Grand and imposing entrance" , "Grand sort of entrance." , "Gate, entrance" , "An imposing door or gate" .)