The phrase "real key" means the most important factor or the crucial thing that can make a situation successful or solve a problem effectively. Full definition
There are few real keys to dog training, whether you want to know how to train a dog to come when called, sit, stop barking or any other behavior. (dogtrainingpost.com)
There are a few real keys to dog training, whether you are trying to train your dog to come when called, sit, stop barking or any other behavior. (ultimatepetwebsites.com)
If you are using real key limes, then zest 2 to punch up the key lime flavor. (dinner-mom.com)