Curved entranceway (4)
I believe the answer is:
arch
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">curved entranceway</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for arch that I've seen before include "Curve spanning an opening" , "Mischievous - shrewd" , "Bridge span" , "Self-consciously playful or teasing" , "Chief - opening with curved top" .)