Riders do get involved in fracas (8)
I believe the answer is:
disorder
'fracas' is the definition.
(thesaurus)
'riders do get involved' is the wordplay.
'get involved' indicates an anagram.
'riders'+'do'='ridersdo'
'ridersdo' with letters rearranged gives 'DISORDER'.
'in' acts as a link.
(Other definitions for disorder that I've seen before include "Although it's only a minor ailment" , "Disturbance of normal working, as of mind or body" , "breach of the peace" , "Commotion" , "complaint" .)