Gymnast’s costume (7)
I believe the answer is:
leotard
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">gymnast's costume</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 leotard that I've seen before include "One-piece garment worn by acrobat" , "Gymnast's tight costume" , "Body suit for dancers" , "Dance/exercise garment" , "Dancers might wear this" .)