What is the noun clause in the sentence "Whatever crawls in is trapped." and the function of the noun clause

The noun clause in this sentence is Whatever crawls in

A noun clause is used to name something when a single word is not enough. It is a dependent clause and it can not stand alone.

A noun clause usually starts with such keywords as: how, that, what, whatever, who, whoever etc.

A noun clause can function as a subject of a verb : Whatever crawls in is trapped, as an object of a sentence, as a subject complement or as a object preposition.