Open shoe (6)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">open shoe</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for sandal that I've seen before include "Wood" , "Openwork shoe" , "Type of footwear" , "Item of footwear" , "One can go on foot" .)
(Other definitions for flip-flop that I've seen before include "Light shoe" , "Informal footwear" , "Shoe held on by a toe-thong" , "Flimsy sandal" , "Rubber sandal" .)