There is no record of when John Clements left East Markham and came to Nottingham. By the year of his 20th birthday he had signed for a Nottingham amateur club called St. Saviour's. and played for them in the 1887–1888 season. In 1888 he was discovered by Notts County and signed for them in October 1888.
John Clements made his League and club debut at Trent Bridge, Nottingham on 27 October 1888. He played left-back. The opponents were Burnley, 4,000 were in attendance. Burnley won the toss and chose ends so that County had to kick into the wind. However, this fact seemed to make little difference to the play. County were two up in 11 minutes, the scorers Harry Daft and Bob Jardine. Later in the first-half Daft and Jardine combined for Jardine to shoot past the Burnley goalkeeper but the 'goal' was disallowed as the referee judged Jardine was off-side. Early in the second-half County goalkeeper, Jack Holland was injured and then Burnley got one back through Jack Yates so, it appeared that Burnley were going to get back into the game. However, ten minutes into the second-half Jardine became the first Notts County player to score a brace in a League match. Soon after he scored the first Notts County League hat-trick. Towards the end of the match Jardine made it four in a match and then Jardine made history. He scored his fifth, Notts County' sixth becoming the first player to score five in a match in a League game. A remarkable achievement. John Clements had a quiet match but made his own bit of history. The first Notts County player to win a match on his debut. Final Score – Notts County 6-1 Burnley.
1888–1889 season
John Clements made his club and League debut on 27 October 1888 at left-back at Trent Bridge, Nottingham for a home match against Burnley. From 27 October 1888 to 16 March 1889 John Clements played 12 League games and three F.A. Cup ties, all at left-back. Having played 12 times at left-back he became the main player in the left-back position for 1888–1889 season. Clements played 12 league matches for Notts County and when he played his team scored 25 goals and conceded 40 out of 73 goals. The 40 goals was the joint third lowest tally by any League club that season. The 73 goals conceded was the worst by any League club in 1888–1889. Notts County finished 11th and had to seek re-election.
1889 onwards
Clements was retained for the 1889–1890 season but was now considered a reserve player. He only appeared in two League games and once in the FA Cup. In seasons 1891-1892 he remained on the Notts County books but did not play in the first team. Clements left Notts County in June 1892 and joined Newton Heath who had just been admitted to the Football League. Clements played in 36 League games and appeared in one FA Cup tie in 1892–1893. In August 1894 Clements transferred from Newton Heath to Rotherham United who were in Football League Division 2. He played only one season at Rotherham. He played 27 League matches, scoring three goals. He also played one FA Cup tie. In May 1895 he transferred to Newcastle United. However, he never played for the first team due to injuries. It is also not recorded when he left Newcastle United.
Life after football
As said Clements date of retirement from football was not recorded. It is not clear what Clements did for a living after leaving football. He eventually moved to ChesterfieldDerbyshire and passed away there in 1945 at the age of 77.