DS vs government agency

DS and government agency both are nouns.

Word	Noun	Adjective	Verb	Adverb
DS	Yes	No	No	No
government agency	Yes	No	No	No

As nouns, government agency is a hypernym of DS; that is, government agency is a word with a broader meaning than DS:

DS: the bureau in the State Department that is responsible for the security of diplomats and embassies overseas
government agency: an administrative unit of government

Other hypernyms of DS include agency, authority, bureau, federal agency, office.

DS (noun)	government agency (noun)
an honorary degree in science	an administrative unit of government
the bureau in the State Department that is responsible for the security of diplomats and embassies overseas