With leading parts of Mike, Rick, Vyvyan and Neil plus Alexei Sayle, ultimately playing scumbags (6)
I believe the answer is:
vermin
'scumbags' is the definition.
I can't explain the rest of the clue.
(Other definitions for vermin that I've seen before include "Rats, mice, foxes and other harmful creatures" , "Harmful or disease-ridden animals" , "Animals and birds of objectionable kind" , "Mice maybe" , "Destructive animals" .)