There is no meaning in what you say. The underlined clause is a/an-

A noun clause is a subordinate clause used as a noun in the sentence.
A noun clause may be used as a subject or direct object of the verb, as a predicate noun, as object of the preposition, or as an appositive.
In the given sentence, the clause what you say serves as the object of the preposition ‘in’.
So, it is a Noun clause.