Based on the sentence, the adverbial clause is "after he finishes football practice". Adverbial clause is a set of words that is usually preceded by subordinating conjunctions such as after, if, etc.It usually answers the question when, where, what, how or by how much.
What does America mean to you? Is it just the red white and blue? Are the stories really true? Just between me and you I believe America is the best anyone could do!