Ready-made house (6)
I believe the answer is:
prefab
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">ready-made house</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for prefab that I've seen before include "Cheap building" , "Building assembled from pre-manufactured parts, in short" , "Building assembled with sections made elsewhere" , "small postwar house" , "British inter-war temporary housing, popularly called" .)