Principal church of a diocese (9)
I believe the answer is:
cathedral
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">principal church of a diocese</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for cathedral that I've seen before include "dramatic murder location" , "Principal 2 down of diocese" , "Carted Hal off to church" , "Where one worships" , "Principal church of see" .)