Charles Cunningham , land agent in Ireland whose surname has come to mean a refusal to do business with another party (7)
I believe the answer is:
boycott
(Other definitions for boycott that I've seen before include "Refuse to deal with - outlaw" , "Blackball" , "Refuse to deal with - Yorkshire and England batsman" , "Refuse to deal with (someone) as a protest" , "Ostracise" .)