Riding costume (5)
I believe the answer is:
habit
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">riding costume</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 habit that I've seen before include "It's worn in order" , "nun gets into" , "Monk's gown or custom" , "Custom, wont" , "Addiction to a drug" .)