Final answer:
The italicized clause 'until you have finished' in the given sentence is an adverb clause that modifies the verb 'will wait' and indicates a time relation.
Step-by-step explanation:
The italicized clause in the sentence 'We will wait until you have finished' is functioning as an adverb clause. This is because it begins with the subordinating conjunction 'until', which is an indicator of time, and it modifies the verb 'will wait' by specifying when the waiting will take place. The clause 'until you have finished' cannot stand alone as a sentence and is dependent on the main clause for its complete meaning, which is a characteristic of a dependent clause.