INS vs federal agency

INS and federal agency both are nouns.

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

As nouns, federal agency is a hypernym of INS; that is, federal 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
federal agency: an administrative unit of government

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

INS (noun)	federal 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