Adjective clauses are dependent clauses that fulfill the role of adjectives. In other words, they modify nouns and pronouns by providing more information about them. Adjective clauses contain a subject and a verb. They also begin with words such as <em>that, where, who, whom</em>, etc. (relative pronouns). In this case, the adjective clause is providing additional information about the football team, by saying that the members were really hungry.
