"Found by the clerk" is the verbal phrase in the sentence "The wallet found by the clerk belongs to my father." It is a past participle type.
A verb phrase refers to the part of a sentence that contains both the verb and either a direct or indirect object (the verb's dependents). Some verb phrases have a single function which means it can act like an adverb or an adjective.
Verbs constitute a link between the subject of the verb and information about that subject.