A grip or control so strong as to stifle or cut off.
For years the company had a stranglehold on the rest of the industry.
Numerous witnesses had come forward at that time to state that they had watched Kelly tackle Symaco and pin her on the floor in a strangle-hold until investigating officers arrived to pry him loose.1979 August 25, Jil Clark, “Police Officer Convicted in Beating of Lesbians”, in Gay Community News, volume 7, number 6, page 1:
1 more example
That record felt like ancient history as the Djokovic of 2011 overcame a slightly edgy start to take a stranglehold on the match.2011 July 3, Piers Newbury, “Wimbledon 2011: Novak Djokovic beats Rafael Nadal in final”, in BBC Sport:
"She does not hold a partner; she strangleholds him. As soon as a man realizes how tightly she holds on, he leaves her."2014, David Richo, When Love Meets Fear: How to Become Defense-less and Resource-full: