If you need to remove contact from deal, go to your deal and click on edit deal (pen icon).
In new screen, next to contact, you will see ‘Delete’ button, and by pressing that button your contact will be removed from the deal.
Click ‘Save’, to apply changes.
Contact deleted using this procedure will only be removed from the deal, but it will remain in your contacts. To remove contact completely from the system, please see this article.