Your clwinding class is syntactically valid.
Your clloss class, on the other hand, has some conceptual errors. I'm going to make one change, replacing the lower-case L property and variable with upper-case L (just personal preference, I avoid using lower-case l because of the ease with which it can be confused with the number 1.)
function objL = clloss (L)
objL = objL.L;
I see three problems here.
The first and most important is that the constructor of a class must return an instance of that class. So objL must be a clloss object. Is it?
The second problem is that when you run this line of code, nothing has assigned a value to objL.L yet so it is a 0-by-0 double array. So the answer to the question I asked in the first problem, "Is it?", is no. As written this constructor returns the 0-by-0 double and MATLAB will error because that is not a clloss object.
The third problem is that you don't use the value the user of the class passed into the constructor. Your mental model may be that because the input argument has the same name as the property that it's automatically assigned into that property; if so that is incorrect.
If your goal is to assign the value the user of the class passed into the constructor into the property then return the object, your constructor should be:
function objL = clloss(L)
objL.L = L;
Now let's look at the property get method for the Dependent property s.
function s = get.s (objL)
s = objL.L + objw.d;
The first part of this is fine. objL will be a clloss object and it has a property L. The second part is not fine. Nowhere in this code do you define objw.
Because of the fact that the definition of the constructor of the clwinding class calls its output argument objw I think you're thinking that this will retrieve "the" value of the d property of clwinding and use it here. But as you've written the clwinding class, each instance of that class can have a different value for the d property. So which clwinding object's d property do you want to use here? Are you guaranteed that one and only one clwinding object exists? Can you create a clloss object and try to access its s property when no clwinding objects exist? Can you try to get the s property when twenty clwinding objects exist?
If d is some sort of constant that has the same value for all clwinding objects, this code can be repaired. Make the d property of the clwinding class a Constant property. Then you can refer to that constant value using the name of the class, regardless of how many (0, 1, 20, etc.) instances of the class exist.
d = 42;
If each clwinding can have a different value for d, you're probably going to need to store the specific clwinding for this clloss object in a property of the clloss object and reference the d property of that clwinding object. Or you're going to need to design some other way to get "the" clwinding for this particular clloss object.