One attempting to lose weight (7)
I believe the answer is:
slimmer
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">one attempting to lose weight</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for slimmer that I've seen before include "More slender" , "in better shape?" , "One losing weight" , "thinner" , "More slenderly built" .)