"secure leash" means to have full control and ensure safety while restraining or controlling something or someone with a leash or similar device. Full definition
The nickel - plated D - ring allows for secure leash attachment. (petbusiness.com)
What makes them unique is that, instead of securing the leash to a collar around the neck, they use a harness that lifts up the dog's rear end when needed, such as when you want to help your dog climb stairs or go up a hill. (pedigree.com)
A good doggy harness should be chew proof, a snug fit and provide a secure leash attachment. (doggytoggery.com)