fill up vs clog

fill up is not a noun while clog is a noun.

Word	Noun	Adjective	Verb	Adverb
fill up	No	No	Yes	No
clog	Yes	No	Yes	No

As verbs, clog is a hyponym of fill up; that is, clog is a word with a more specific, narrower meaning than fill up:

fill up (noun)	clog (noun)
	a dance performed while wearing shoes with wooden soles; has heavy stamping steps
	any object that acts as a hindrance or obstruction
	footwear usually with wooden soles

fill up (verb)	clog (verb)
make full, also in a metaphorical sense	impede with a clog or as if with a clog
become full	fill to excess so that function is impaired
eat until one is sated	coalesce or unite in a mass
fill or stop up	become or cause to become obstructed
	impede the motion of, as with a chain or a burden
	dance a clog dance