And in another deal involving a former Blues centre-back, Sky Sports are reporting the Seagulls have agreed a £22m fee for Adam Webster.
He is reportedly due at Brighton for a medical today before he seals a club-record move to the Amex Stadium from Bristol City.
Webster, from West Wittering, made his Pompey debut as a 17-year-old in a 1-0 Championship defeat to West Ham in January 2012.
He’d go on to make 85 appearances in total, scoring five goals, before he transfered to Ipswich in June 2016 as part of the deal that brought Clarke to Fratton Park.
The 24-year-old featured 47 times for the Robins last season as they narrowly missed out on a Championship play-off spot.
Clarke, meanwhile, has been identified by new Rams boss Phillip Cocu as a player to aid Derby’s Championship promotion hopes.
Pompey’s player of the year last season was Brighton manager Graham Potter’s first summer signing - penning a four-year deal after moving for a fee believed to be around the £4m mark.
However, despite already impressing at the Premier League outfit, Potter believes a season in the Championship would aid his development.
It is believed Clarke, who made 60 appearances for Kenny Jackett’s side last term in League One, travelled to the East Midlands on Thursday to conclude negotiations.
In total, the centre-half made 175 appearances for the Blues, scoring nine goals.