Top of a house (4)
I believe the answer is:
roof
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">top of a house</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for roof that I've seen before include "Topping structure" , "Upper limit; house top" , "hit by someone in a temper" , "Part of mouth" , "Top covering of a building or vehicle" .)