Curved gateway (4)
I believe the answer is:
arch
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">curved gateway</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 "Embow" , "one that may have fallen" , "Vaulted opening" , "Affectedly playful like curved structure" , "Vault; roguish" .)