belief vs first blush

belief and first blush both are nouns.

Word	Noun	Adjective	Verb	Adverb
belief	Yes	No	No	No
first blush	Yes	No	No	No

As nouns, first blush is a hyponym of belief; that is, first blush is a word with a more specific, narrower meaning than belief:

Other hyponyms of belief include presence, effect, hunch, intuition, suspicion.

belief (noun)	first blush (noun)
any cognitive content held as true	at the first glimpse or impression
a vague idea in which some confidence is placed