Answer:
Subordinate clause.
Explanation:
The main clause is a type of clause which is consisted of a subject and a verb and it can function on its own, it even can represent a sentence.
The subordinate clause is a type of clause that can not function alone, usually, it complements the main clause, which we, in this specific case, miss. What we also can notice from the given clause is that it starts with a relative pronoun which, the subordinate clauses are characterized by starting with a relative pronoun (whose, whoever, that...) or a subordinate conjunction (since, because, until...).
