EXCLUSIVE: Christina Aguilera on Her 'Tough' 1-Year-Old Daughter Summer: 'I'm Going to Have a Heart Attack!'

'The Voice' coach gushes about her adorable baby girl

Christina Aguilera may be a female fashion icon, but when it comes to 1-year-old daughter Summer Rain, The Voice coach loves nothing more than dressing her darling daughter in boys' clothing.

"I like putting pink Converse and stuff [on her], but I totally have Max hand-me-downs that I give to her because there's nothing cuter," Aguilera told ET's Sophie Schillaci at Monday's taping of The Voice, referring to the old outfits of Summer's 8-year-old brother, Max. "She’s got this cute blonde hair, big blue eyes and she’s very girly, but then to dress her up in boy gear is so cute. She's a tough girl!"

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Tough indeed! It sounds like Summer is turning into a bit of a tomboy as she nears her second birthday in August. Aguilera admits the tot is not only giving Max (from Aguilera's previous marriage to Jordan Bratman) a run for his money, but causing constant parental concern as well.

"She's climbing everything," shared the 35-year-old singer, who’s engaged to Summer's dad, 31-year-old Matthew Rutler. "Climbing the walls… she wants to be just like her parkouring brother. I’m going to have a heart attack!"

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The singer also opened up about her fearless fashion choices and what makes her feel hot. Wearing a Cosabella mesh top, Marc Jacobs jacket, Gucci pants and Wythe pants to The Voice on Monday evening, she confessed swapping her glam threads for a bathrobe at the end of the night is what makes her feel sexy.

"When I can take all of it off and be in my bathrobe. Au naturel!" she exclaimed, before adding: "Getting all dressed up... thank God for hair and makeup people. They help you bring alive this sleeping character within yourself. I love dress-up – you can tell from my video work, tours, circus experiments and everything from my past. I love the essence of theatrics and dressing up, which you can see in my performance with my team from last week. I love having fun like that and [to] not take fashion so seriously. It should feel theatrical, fun and artistic."

As for Aguilera's next big project -- an album! -- get the latest details in the the video below.

Additional reporting by Sophie Schillaci