Roof (4)
I believe the answer is:
dome
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">roof</span>' is the definition.<br/ ><span class="explanation-format__explanation">(dome is a kind of roof)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for dome that I've seen before include "Head" , "Curved roof" , "Rounded roof; Greenwich tent" , "Hemispherical roof" , "Rounded vault of a roof" .)