Former Leeds United man Clarke spent the second half of last season on loan at the Stadium of Light and helped Sunderland to win promotion back to the Championship.
Alex Neil is keen to have the winger back and with Clarke surplus to requirements for Antonio Conte in north London a deal has been done.
Clarke will complete his switch to Sunderland within the next 24 hours and has also agreed to put pen to paper to a four-year contract with the club.
The deal will keep Clarke at Sunderland until the summer of 2026.
Clarke, 21, came through the youth ranks at Leeds and was then sold to Tottenham in 2019 for an initial £10m.
He struggled for game time in north London and Tottenham sent him out on loan stints to QPR and Stoke City, prior to his spell with Sunderland.
The winger will look to kick on with his development in the north east as Sunderland gear up for a season of Championship football.
