Most curious (6)
I believe the answer is:
oddest
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">most curious</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 oddest that I've seen before include "Strangest" , "Most strange or curious" , "Most peculiar or strange" , "Most rum" , "Most strange or uneven" .)