CLOS question

I have what seems like a familiar CLOS question, but a quick Google
search doesn't turn up an answer: I have a method, m, and an after
method for it. The after method is specialized on class c. I'd like
to define a class d that inherits c, and have instances of d behave
just like instances of c *except* for that single after method.

I don't believe that I can prevent the after method for class c from
being run when m is called on an instance of d. (Though it would be
convenient if I were wrong about this.) My question is about the
choices for design. I could break class c into two classes, c1 and
c2, and only define the after method for c2, and have d inherit c1,
but I'm wondering if there are other reasonable designs.
.