FDA vs government agency

FDA and government agency both are nouns.

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

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

FDA: a federal agency in the Department of Health and Human Services established to regulate the release of new foods and health-related products
government agency: an administrative unit of government

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

FDA (noun)	government agency (noun)
a federal agency in the Department of Health and Human Services established to regulate the release of new foods and health-related products	an administrative unit of government