tug-of-war vs struggle

tug-of-war and struggle both are nouns.

Word	Noun	Adjective	Verb	Adverb
tug-of-war	Yes	No	No	No
struggle	Yes	No	Yes	No

As nouns, struggle is a hypernym of tug-of-war; that is, struggle is a word with a broader meaning than tug-of-war:

Other hypernyms of tug-of-war include battle, conflict.

tug-of-war (noun)	struggle (noun)
any hard struggle between equally matched groups	strenuous effort
a contest in which teams pull of opposite ends of a rope; the team dragged across a central line loses	an energetic attempt to achieve something
	an open clash between two opposing groups (or individuals)

tug-of-war (verb)	struggle (verb)
	be engaged in a fight; carry on a fight
	to exert strenuous effort against opposition
	climb awkwardly, as if by scrambling
	make a strenuous or labored effort