Church changing room (6)
I believe the answer is:
vestry
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">church changing room</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 vestry that I've seen before include "Church sacristy" , "Church room where clergy dress themselves" , "Part of church used as an office" , "Small room attached to church" , "Storage and dressing room in a church" .)