late-night hour vs hour

late-night hour and hour both are nouns.

Word	Noun	Adjective	Verb	Adverb
late-night hour	Yes	No	No	No
hour	Yes	No	No	No

As nouns, hour is a hypernym of late-night hour; that is, hour is a word with a broader meaning than late-night hour:

Other hypernyms of late-night hour include time of day.

late-night hour (noun)	hour (noun)
the latter part of night	distance measured by the time taken to cover it
	a period of time equal to 1/24th of a day
	clock time
	a special and memorable period