Clayton signed for Doncaster Rovers in January 2022, Bradford City took over his contract a year later, and he spent the 2023–24 season with Rochdale and began the following campaign with Liversedge before taking up a player/coach role with Matlock Town.

[5] Given the number 31 shirt for the 2008–09 season,[6] Clayton was an unused substitute in the Premier League match against West Bromwich Albion in December 2008,[7] and again in an FA Cup tie against Nottingham Forest in January 2009.

[4] After seeking the advice of his teammate Craig Bellamy,[9] Clayton joined League One club Carlisle United on 2 November 2009 on loan until January 2010.

[12] Clayton joined Championship club Leeds United on a month's loan on 6 August 2010,[17] and made his debut the following day as a 76th-minute substitute in a 2–1 home defeat against Derby County.

[18] Having got no closer to Leeds' first team, Clayton joined another League One club, Milton Keynes Dons, on 24 March on loan until the end of the season.

[18] MK Dons manager Karl Robinson felt Clayton was one of the better players in League One and would re-sign him if the opportunity arose, but expected him to make a success of the coming season with Leeds.

[26] After first-choice midfielders Neil Kilkenny and Bradley Johnson both left Leeds United in the 2011–12 pre-season, Clayton declared himself ready to challenge for a place.

[30] Having come close to scoring his first Leeds goal with "the most audacious of attempts from distance which almost caught out" Middlesbrough's goalkeeper, Carl Ikeme, on 13 August,[31] he succeeded a week later with a late equaliser against West Ham United;[32] the Yorkshire Evening Post had suggested that facing an opposing midfield as strong as West Ham's would be "the essence of an acid test" for any aspiring midfielder.

[43] He made his Huddersfield début in the League Cup first round 2–0 away defeat to Preston North End on 13 August 2012, playing the full 90 minutes of the game.

[47] On 13 August 2014, Clayton signed a four-year deal with Middlesbrough after a long transfer process for an undisclosed fee believed to be £1.5 million plus add-ons.

[49] Adam Clayton became an integral player in the Middlesbrough midfield under manager Aitor Karanka, forming a formidable partnership alongside club captain Grant Leadbitter.

[50] With the arrival of Marten de Roon in the summer of 2016, it was reported that Clayton and Leadbitter could leave Middlesbrough, though they both stayed, as Karanka promised the midfield duo game time in the Premier League.

[51] Garry Monk replaced Karanka as manager for the forthcoming Championship season, and brought in two new central midfielders Lewis Baker and Jonny Howson, though Clayton continued to play regular first team football.

[58] He began the season well,[59] but conceded a penalty from which Sheffield Wednesday inflicted Birmingham's first league defeat under Karanka,[60] and was sent off three days later near the end of the visit to Norwich City, who promptly scored a winning goal.

[67][68] Having played little under new head coach Danny Schofield, Clayton joined divisional rivals Bradford City on 19 January 2023 on a short-term contract until the end of the season.