stran ‧ gle ‧ hold /ˈstræŋɡ ə lhəʊld $ -hoʊld/ BrE AmE noun [countable]
1 . [usually singular] complete control over a situation, organization etc
stranglehold on
Just a few firms have a stranglehold on the market for this software.
break/loosen the stranglehold of somebody (=stop someone having complete control)
2 . a strong hold around someone’s neck that stops them from breathing