The turf green for this British activity (6)
I believe the answer is:
racing
'the turf' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for racing that I've seen before include "operating at great speed" , "Competing in speed contests" , "activity on track" , "Dashing" , "going very fast" .)