Ship carrying less ballast? (7)
I believe the answer is:
lighter
'ship' is the definition.
(thesaurus)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for lighter that I've seen before include "relieved of some cargo?" , "carrying less cargo?" , "Barge; igniter" , "carrying less weight" , "- boot; - bun; - ware" .)