I am really worried it will fly away if let out. Sometimes, I will put a shell nut, waltnus, pecan, almond etc for it to bite n play in replaced of a toy. Think i always have too much to ask at one go. There are several good books about eclectus as well. Even almonds, which are generally considered to be soft shelled nuts, are too hard for most eclectus to crack open.
Walnuts are too large, and too hard.
What we do is crack open a few almonds and let the bird eat them - that way they know there is a delicious nut inside the shell and how to pick it out of the shell. This way the nut can be a toy and food at the same time. Crack a walnut open and let the bird pick the nutmeat out of the shell. Like the almond, the walnut becomes a food that is also a toy. Even if you only crack part way, so the bird can dig into the nut and get the rest.