The singer fell into the bottom two with Union J, performing a rendition of Wires by Athlete while the group sang Snow Patrol’s Run.
Only Clark’s mentor Nicole Scherzinger chose to save him, while Gary Barlow, Tulisa Contostavlos and Louis Walsh saved Union J, sending Clark home.
Scherzinger said that while Union J’s performance was “very moving”, she had to send them home as she still believed in Clark.
Walsh said that Clark was a “fantastic guy” and “brilliant fun”, but said he thought Union J won the sing-off.
Barlow, who had been critical of Clark during this year’s series, said that he was a “brilliant contestant”.
Contostavlos had the final vote and went for Union J as they had the potential to sell more records.
On ITV2’s The Xtra Factor, Clark told hosts Caroline Flack and Olly Murs that he felt like a weight had been lifted off his shoulders.
He joked: “I feel like I’ve just been let out of prison.”
Earlier in the week Clark had posed with his mentor in the famous Stonewall “Some people are gay, get over it” t-shirts.