|Origin:||Probably from clench|
to finally agree on something or get something after trying very hard:
a young salesman eager to clinch the deal
clinch a match/championship/victory etc
A last-minute touchdown clinched the game.
if an event, situation, process etc clinches it, it makes someone finally decide to do something that they were already thinking of doing:
We'd talked about moving, and the burglary clinched it for us.
if two people clinch, they hold each other's arms tightly, especially when fighting