Smoker's accessory is less burdensome (7)
I believe the answer is:
lighter
'smoker's accessory' is the definition.
(a cigarette lighter)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for lighter that I've seen before include "Barge; one needed by smoker" , "Less weighty" , "Open boat - spill" , "- boot; - bun; - ware" , "Boat for heavy loads and fire igniter" .)