Least modest (7)
I believe the answer is:
vainest
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">least modest</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for vainest that I've seen before include "Most proud" , "Arrogant in the extreme" , "Most fond of one's own looks" , "emptier than all the others" , "Most conceited" .)