Classical performance hall
I believe the answer is:
odeum
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">classical performance hall</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 odeum that I've seen before include "theatre in Athens?" , "Roman theatre" , "place of performing music" , "concert hall" , "Greek building for music" .)