Extremely overweight (5)
I believe the answer is:
obese
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">extremely overweight</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 obese that I've seen before include "Needing to lose weight" , "Excessively fat" , "Extremely fat" , "Very big" , "Grossly overweight" .)