Priest's cassock (7)
I believe the answer is:
soutane
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">priest's cassock</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 soutane that I've seen before include "Garment for a priest" , "Catholic priest's cassock" , "item of clothing" , "Long plain robe for a priest" , "Garb for priest" .)