Painting with three panels (8)
I believe the answer is:
triptych
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">painting with three panels</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 triptych that I've seen before include "Three-part picture" , "Picture with three sections" , "Artistic work on three panels" , "panel" , "Three-panelled painting" .)