The condition of being clear or transparent is transparency. The transparency of your car's windshield might be affected by how badly your car needs to be washed.
Something has transparency if you can see through it, like the ice on the top of a frozen lake or a glass. Transparency can also refer to a figurative kind of clearness or openness, which is what people mean when they talk about "government transparency." If you can see clearly, without anything being hidden, what you're looking at (or through) has transparency. Its root is the Latin word transparentem, which means "see light through."