fifth column vs social unit

fifth column and social unit both are nouns.

Word	Noun	Adjective	Verb	Adverb
fifth column	Yes	No	No	No
social unit	Yes	No	No	No

As nouns, social unit is a hypernym of fifth column; that is, social unit is a word with a broader meaning than fifth column:

fifth column: a subversive group that supports the enemy and engages in espionage or sabotage; an enemy in your midst
social unit: an organization regarded as part of a larger social group

Other hypernyms of fifth column include unit.

fifth column (noun)	social unit (noun)
a subversive group that supports the enemy and engages in espionage or sabotage; an enemy in your midst	an organization regarded as part of a larger social group