Wikipedia says :
The kidneys secrete a variety of hormones, including erythropoietin, and the enzyme renin.
Can a substance be both an enzyme and a hormone ? Why is renin both an enzyme and a hormone ?
Yes, something can be both a hormone and an enzyme. There are a group of hormones known as peptide hormones. These are proteins (such as enzymes) that act as hormones indirectly (and maybe directly too?). A hormone is a chemical secreted by a cell that has some effect on another cell elsewhere in the body. In this case, the chemical just happens to be an enzyme. You can read about them on Wikipedia
Renin is secreted by the kidney, but its involved in arterial vasoconstriction (outside of kidney cells), so it is a hormone. And its also a peptide/enzyme, so it is considered both a hormone and an enzyme
Hormone is just a different class of protein and is not usually an enzyme. Peptide hormones have no catalytic potential and serve only as signaling ligands.
There can be secreted enzymes which is common in the digestive tract but these are not called hormones. Hormone is purely a signaling molecule.