The phrase "smooth fox" refers to someone who is clever, calm, and skilled at solving problems or navigating difficult situations. They are like a clever fox that moves smoothly and effortlessly. Full definition
Until 1984, when they were designated separate breeds, the wire fox terrier was considered a variety of smooth fox terrier. (dogcare.dailypuppy.com)
I live with smooth fox terriers and have been training formally since 1996. (thedogtrainingsecret.com)
Over 50,000 dogs have been successfully potty trained with our world - famous indoor dog potty, called the Potty Training Puppy Apartment, including smooth fox terriers. (modernpuppies.com)