Thinnest (7)
I believe the answer is:
leanest
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">thinnest</span>' is the definition.<br/ ><span class="explanation-format__explanation">('lean' can be a synonym of 'thin')</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for leanest that I've seen before include "most meagre type" , "Poorest-quality" , "Most thin" , "Most unproductive" , "Least fat" .)