INS vs government agency

INS and government agency both are nouns.

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

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

INS: a former agency in the Department of Justice that enforces laws and regulations for the admission of foreign-born persons to the United States
government agency: an administrative unit of government

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

INS (noun)	government agency (noun)
a former agency in the Department of Justice that enforces laws and regulations for the admission of foreign-born persons to the United States	an administrative unit of government