cluster vs tussock

cluster and tussock both are nouns.

Word	Noun	Adjective	Verb	Adverb
cluster	Yes	No	Yes	No
tussock	Yes	No	No	No

As nouns, tussock is a hyponym of cluster; that is, tussock is a word with a more specific, narrower meaning than cluster:

Other hyponyms of cluster include knot, swad, tuft.

cluster (noun)	tussock (noun)
a grouping of a number of similar things	a bunch of hair or feathers or growing grass

cluster (verb)	tussock (verb)
gather or cause to gather into a cluster
come together as in a cluster or flock