Lower part of an interior wall (4)
I believe the answer is:
dado
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">lower part of an interior wall</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 dado that I've seen before include "skirting material" , "Decorative wall border" , "Architectural feature" , "Low wall panel" , "Lower part of the wall of a room" .)