Less weighty (7)
I believe the answer is:
lighter
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">less weighty</span>' is the definition.<br/ ><span class="explanation-format__explanation">('light' can be the opposite of 'weighty' so perhaps 'lighter' is reasonable for 'less weighty')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for lighter that I've seen before include "Barge; igniter" , "- boot; - bun; - ware" , "Boat with a flat bottom for carrying heavy loads" , "Supply boat" , "carrying less weight" .)