incumbentin·cum·bent1 /ɪnˈkʌmbənt/ noun [countableC]1the person who has a particular job or position at this time, rather than one who wants it or may have it laterNine out of ten incumbents who seek re-election win.
2the company that has work from a particular customer at this timeThe company decided to move the account from the incumbent, Grey Advertising, to another agency.