Curved roof (4)
I believe the answer is:
dome
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">curved roof</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 dome that I've seen before include "Cupola - millennium building" , "Rounded roof with circular base" , "Head" , "Curved roof" , "Mode or arched roof" .)