Barge carrying less weight (7)
I believe the answer is:
lighter
This clue is a double definition.
'barge' is the first definition.
(I know that barge can be written as lighter)
'carrying less weight' is the second definition.
(lighter means less heavy)
(Other definitions for lighter that I've seen before include "Barge; flame producer" , "carrying less cargo?" , "carrying less weight" , "Canal boat with a flat bottom" , "Barge - less heavy" .)