The 25-year-old central midfielder has agreed a two-year deal at the Matchroom Stadium having made thirty-nine appearances at Fir Park last season.
Clay, who was born in Nottingham, started out at Chesterfield where he graduated through the Spireites youth system and named the club’s young player of the year for the 2008/09 season.
The midfielder then experienced his first taste of first-team involvement for their game against Torquay United in January 2010, in which he was an unused substitute.
Due to his impressive record for the youth team, Clay was rewarded with his first professional contract in June 2010 and went on to make his Chesterfield debut in September of that year as a substitute against Cheltenham Town.
Clay then went to gain further experience on loan at Conference (National League) Premier sides Barrow AFC and Alfreton Town respectively, and following twenty-three appearances for Chesterfield during the 2012/13 season, departed the Proact Stadium to join York City in May 2013.
Following six months with the Minsterman, however, Clay found himself on the move again as he spent short spells at both FC Halifax Town and Worksop Town before signing a one-year deal at Grimsby Town ahead of the 2014/15 season following a successful trial.
Clay’s switch to the Mariners proved to be a wise decision, as the midfielder racked up a total of forty-seven appearances to help Grimsby reach the Promotion Final.
Having agreed a new deal during the summer of 2015, Clay and Grimsby then went one better as achieved promotion back to the Football League with a 3-1 victory over Forest Green Rovers in the Conference Promotion Final, with the midfielder totting up a total of forty-four appearances.
Clay’s performances throughout the 2015/16 season saw the midfielder selected for the England C team, and in August 2016 made the move to Scotland to sign for Motherwell following a successful trial.