street fighter vs fighter

street fighter and fighter both are nouns.

Word	Noun	Adjective	Verb	Adverb
street fighter	Yes	No	No	No
fighter	Yes	No	No	No

As nouns, fighter is a hypernym of street fighter; that is, fighter is a word with a broader meaning than street fighter:

street fighter: someone who learned to fight in the streets rather than being formally trained in the sport of boxing
fighter: someone who fights (or is fighting)

Other hypernyms of street fighter include battler, belligerent, combatant, scrapper.

street fighter (noun)	fighter (noun)
a contestant who is very aggressive and willing to use underhand methods	a high-speed military or naval airplane designed to destroy enemy aircraft in the air
someone who learned to fight in the streets rather than being formally trained in the sport of boxing	someone who fights (or is fighting)
	someone who fights for a cause