What is a clause?
A clause is a group of words that contains a subject and a predicate. The clause may be dependent, which means it does not express a complete thought and cannot stand alone, or it might be independent clause, which means it does express a complete thought and complete thought and can stand alone by itself.
Dependent clause: because the work was piling up
Independent clause: The work was piling up.
Answer 1 is good, but you may have been asking about the difference between a clause and a phrase, which does not have a subject-verb combination:
The game was over. Independent clause
After the game was over. Dependent clause
After the game. Prepositional phrase (no verb)