Collide briefly with runners when cycling (4)
I believe the answer is:
kiss
'collide briefly with' is the definition.
(kiss can mean to brush against or hit softly)
I cannot understand how the rest of the clue works.
(Other definitions for kiss that I've seen before include "Smooch" , "Evidence of romance" , "Snog" , "Greet with lips" , "Embrace" .)