Two-piece bathing costume (6)
I believe the answer is:
bikini
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">two-piece bathing 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 bikini that I've seen before include "gear in two pieces" , "tests were carried out here" , "Women's tiny bathing costume" , "Atoll and skimpy swimsuit" , "Small two-piece bathing costume" .)