Wall plaster (6)
I believe the answer is:
stucco
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">wall plaster</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 stucco that I've seen before include "White plaster covering for exterior walls" , "Plaster for coating outside walls" , "wall-covering" , "Fine type of plaster" , "Fine decorative plaster" .)