Two-piece swimming costume (6)
I believe the answer is:
bikini
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">two-piece swimming 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 "Small two-piece bathing suit" , "Infamous atoll" , "Atoll and swimming costume" , "Skimpy two-piece swimsuit" , "two-piece outfit" .)