Clancy played for the Republic of Ireland under-19 team. He played for his home town club Trim Celtic and then Belvedere before signing for Millwall. He then had spells in English non-league football with Walton & Hersham, Weymouth and Fisher Athletic. Clancy joined Scottish Premier League club Kilmarnock in early 2007 on amateur forms. He then agreed a one-year professional contract with Kilmarnock in June 2007. Clancy made his debut at left full back away to Gretnain September and made enough appearances during the 2007–08 season to trigger an automatic extension to his contract. His progress at Kilmarnock was hindered by a series of injuries, however, as he missed over four months after suffering an ankle ligament injury in April 2008. Clancy also missed pre-season training in 2008–09 due to injury. He made a first team comeback in a goalless 0–0 draw at Aberdeen in February 2009. Clancy played regularly for Kilmarnock towards the end of the season and agreed a new two-year contract with the club. He did not play regularly during the 2010–11 season, as manager Mixu Paatelainen used Jamie Hamill as his regular right back. Later in the season, he scored an own goal which gave Rangers a 2–1 victory. Clancy made 73 appearances for Killie in total. Manager Kenny Shiels allowed Clancy to leave the club in order to rebalance his defensive options, with Ryan O'Leary out injured. Clancy moved to Motherwell in August 2011 and agreed a one-year deal. Motherwell signed Clancy to cover for the long-term injury suffered by Steven Saunders. He played regularly in central defence for Mothewell, alongside Shaun Hutchinson. He also played both full back positions during the season. At the end of the season, Clancy rejected a new contract from Motherwell. Clancy signed a two-year contract with Hibernian in June 2012. Clancy scored the first goal in a 2–2 draw against Celtic on 1 September, when he took advantage of a defensive mix-up. It was the first goal he had scored since playing in English non-league football, over six years previously. Clancy played regularly for Hibs before suffering from a groin injury that required specialist advice. He continued to suffer from injury problems and was released by Hibs in January 2014. On 28 February 2014, Clancy signed for St Johnstone on a contract until the end of the 2013–14 season despite interests from Derry City. Clancy scored his first goal for the club, in a 3–3 draw against Celtic on 7 May 2014, which turns out to be his last appearance for the club. Clancy sustained a serious Achilles injury during training and needed an operation that ruled him out of the final of Scottish Cup. At the end of the 2013–14 season, Clancy was among four players to be released by St Johnstone. Tim returned home to sign for Shamrock Rovers in February 2015 . In July 2015 Tim went on loan to Sligo Rovers until November. In January 2016 Tim signed permanently for Sligo but left the club in June. On 28 June Tim went on trial at Bray Wanderers during their 1-0 friendly win against Falkirk. On 30 June Tim signed permanently for Bray making his competitive debut vs Bohemians. On December 5, 2017 Clancy was appointed as Manager of League of Ireland First Division side Drogheda United. This is his first role in management and will be assisted in the role by newly appointed Director of Football Dave Robertson.
