clock time vs hour

clock time and hour both are nouns.

Word	Noun	Adjective	Verb	Adverb
clock time	Yes	No	No	No
hour	Yes	No	No	No

As nouns, hour is a hyponym of clock time; that is, hour is a word with a more specific, narrower meaning than clock time:

Other hyponyms of clock time include SCLK, spacecraft clock time, prime time, time of day.

clock time (noun)	hour (noun)
a reading of a point in time as given by a clock	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