Question

is the group of words in bold a phrase or a clause?
the u.s. marshals service is a federal law enforcement agency that handles numerous responsibilities, including the apprehension and transportation of federal fugitives.

Explanation:

To determine if the bolded group of words (assuming it's "federal law enforcement agency") is a phrase or clause: A phrase lacks a subject - verb pair, while a clause has both. "Federal law enforcement agency" has no subject - verb relationship, so it's a phrase.

Answer:

It is a phrase.