Cycling group stops bunch of traffic things going overboard (6)
I believe the answer is:
jetsam
'cycling' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for jetsam that I've seen before include "Unwanted stuff thrown overboard" , "it is scattered at sea" , "Goods thrown into the sea" , "Unwanted material thrown overboard" , "Goods washed ashore from shipwreck" .)