A clause is a group of words with a subject and verb. That kind of clause is handy when talking about grammar. Another kind of clause is a provision or stipulation in a legal contract.
Clause is a noun that comes from the old French clause, which, if we trace it way back, comes from the Latin clausula, “the end, a closing termination.” Around 1300, the “ending” implication of the word began to fade and was replaced by “article or section of a text.” In the grammatical sense, every sentence must have at least one independent clause. And in the legal sense, documents like prenuptial agreements or job contract often contain clauses.