Speaking of McEntire's big night, Clarkson marveled at the magnitude of the honor.
"It's just such a prestigious award to get in the first place, so that's amazing. Especially [since] I thought maybe she already had this. Like, I didn't know," Clarkson admitted to ET of her former mother-in-law and close friend. "So whenever they called and asked if I would sing with her I was like, 'Of course!'"
"[I'm] insanely busy but I'd do anything for her because she's really been not only such a cool idol musically, but a really great friend and a great family member," Clarkson continued. "She's just a really impeccable human."
Check out Clarkson's performance when the 41st Annual Kennedy Center Honors ceremony airs Dec. 26 on CBS.