Sammy Clingan became Norwich City's first signing of the 2008 summer when on 17th June 2008, he agreed to join the Canaries on 1st July 2008 after his contract with Notts Forest expired.

The Northern Irish midfielder began his career in August 2001 as a youth trainee at Wolverhampton Wanderers. He captained Wolves reserves in 2003/04, but never broke into the first team. He was loaned out to Chesterfield on two occasions to gain experience and made 29 appearances, scoring three times, between October 2004 and January 2006

In early 2006, Nottingham Forest confirmed their interest in him. The original deal fell through because of the existing loan deal with Chesterfield, but when his loan period ended on 15 January, Forest made a second bid. Despite the player's wish to remain at Chesterfield, the Spirerites were unable to match the offer, and Clingan joined Forest on the 23rd January 2006 for an undisclosed fee, making his debut in a 2-0 defeat to Barnsley. He went on to make 85 appearances for Forest and attracted interest from QPR and Ipswich before he signed for Norwich.

Clingan has represented Northern Ireland at Under 17, Under 19, Under 21 and full international levels. He gained six Under 21 caps and captained the side. He made his senior debut at the Giants Stadium in New York against Uruguay during Northern Ireland's two-game tour of the USA in May 2006. His first competitive senior cap came in the 3-0 home defeat by Iceland on 2nd September 2006

Following Norwich's relegation to League One at the end of the 2008/9 season, Clingan's future was the subject of much speculation. On 11th June 2009, it was speculated that he would join Coventry in return for £1million and striker Robbie Simpson. Instead he joined the Sky Blues on 24th July 2009 for an undislosed fee without Simpson coming the other way. He signed a three year contract with Coventry.

Clingan was not in the line-up for Coventry when they lost to Doncaster on 21st April 2012 and were relegated to League One. He left the club at the end of May 2012 when his contract expired. He had made 98 league appearances for Coventry, scoring seven goals.

Clingan joined Crystal Palace on trial in mid-July 2012.

At the end of September 2012, he joined Charlton on trial, playing as an over-age but non-contract player in their Development Squad's clash with Swansea on 2nd October 2012.

He joined Doncaster Rovers on a rolling month-to-month deal on 26th October 2012. He made nine appearances for Rovers before departing in December 2012. On 29th January 2013, Sammy signed for Scottish side Kilmarnock on an eighteen month contract.

Clingan was released by Kilmarnock at the end of the 2014/15 season.He had made 60 appearances for Kilmarnock.

On 14th July 2016, he signed for Northern Irish Premier League side Linfield, managed by his former international colleague David Healy. Clingan left Linfield at the end of the 2016-17 season, and on 8 August 2017 it was announced that he had signed for Glenavon. His first goal for the club came in a 6-1 win over Ballymena United.

He retired at the end of the 2020/21 season.following a knee injury that required surgery.