Clark, who has divided public opinion with his exotic outfits and outrageous performances on the talent show, knocked out Adam Burridge, Nathan Fagan-Gayle and James Quickenden and was selected for the Final 12.
Defending her choices, Scherzinger told The Xtra Factor that she believed the Essex singer wouldn't let her down.
"He's done so much work, he's improved so much," she said.
"Someone who is willing to work that hard, it means that much to them, you know you're going to get everything out of them."
Recalling Rylan's tearful and over-the-top response to finding out that he had got through, the Pussycat Dolls star joked: "I took a break and had a dinner - he was still crying. I rode a camel, came back - and he was still crying."
Scherzinger's other finalists are James Arthur and Jahmene Douglas.
The X Factor Live Shows start this weekend on ITV1.
[X Factor Final 12 - Photo Gallery]
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