Trade is sort of light (7)
I believe the answer is:
traffic
I believe this clue is a double definition.
'trade' is the first definition.
(trafficking is a kind of trading)
'is sort of light' is the second definition.
(I've seen this before)
(Other definitions for traffic that I've seen before include "Dishonest trading" , "dealings" , "Illegally push" , "Deal illegally , in drugs say" , "Trade (in cars?)" .)