Singlet (4)
I believe the answer is:
vest
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">singlet</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for vest that I've seen before include "Undergarment to put in right of possession" , "Thesaurus compiler" , "Undergarment for upper body" , "Waistcoat (in USA)" , "Upper undergarment, singlet" .)