Chalkboard
I believe the answer is:
slate
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">chalkboard</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for slate that I've seen before include "A roof-tile; criticise heavily" , "Run down" , "Roofing material or credit recorder" , "Criticise harshly" , "Rubbish" .)