Which words in the sentence are the adverb clause?
wait with your friend near the front of the store while i finish grocery shopping.
a. while i finish grocery shopping
b. near the front of the store
c. wait with your friend

Adverb clauses answer the questions when, how, where, and why. It's easy to spot as it is usually preceded with a subordinating conjunction. Subordinating conjunctions include after, because, since, where, while, etc. Reviewing the choices:

(b) near the front of the store- near isn't a conjunction. It's an adjective
(c) wait with your friend- wait isn't a conjunction. It's a verb.

However, (a) while I finish grocery shopping is introduced by the subordinating conjunction "while". It is then the adverb clause of time.