Following a loan spell at Notts county, Clarke-Salter returned to Chelsea and signed a new four-year deal in July 2017. He was given the number 35 jersey and made his first appearance of the 2017–18 season during Chelsea's 5–1 EFL Cup victory over Nottingham Forest. On 8 January 2018, Clarke-Salter joined Championship club Sunderland on loan for the remainder of the campaign. Just under a week later, he made his debut during Sunderland's 4–0 away defeat against Cardiff City, playing the full 90 minutes. On 24 February 2018, Clarke-Salter was shown a red card for what BBC Sport reporter saw as a "nasty late challenge" on Middlesbrough's Adama Traoré in a match that ended as a 3–3 draw. In his first game back from suspension, Clarke-Salter was dismissed again after receiving a second yellow card in a 2–0 defeat against Preston North End. He finished the loan spell with nine appearances. 2018–19 season: Loan to Vitesse On 2 July 2018, Clarke-Salter agreed to join Dutch side Vitesse on a season-long loan. 2019–20 season: Loan to Birmingham City Clarke-Salter signed for Championship club Birmingham City on 24 July 2019 on loan for the season. He made his debut on 6 August in the EFL Cup first round visit to Portsmouth. Manager Pep Clotet fielded an inexperienced team, and Clarke-Salter played the whole of the 3–0 defeat. He did not play in the Championship until 1 October, taking the place of the injured Marc Roberts in the starting eleven for the 1–0 defeat away to Wigan Athletic. According to the manager, "he played with a lot of maturity, he was very focused, he dealt very well with the physicality of the game and worked very well with Harlee [Dean] as well. He also covered the line very well. I think on the ball he was very good as well so it was a very positive game for him." His performance was similarly positive in his next appearance a month later, when he replaced the suspended Dean for a 1–0 defeat at home to Fulham. He scored his first goal for Birmingham in a 1–1 draw with Millwall on 30 November. 2020–21 season: Loan return to Birmingham City On 16 October 2020, Clarke-Salter returned to Birmingham City on loan for the remainder of the season. A calf injury kept him out until after the international break, and he made his debut on 24