police work vs roundup

police work and roundup both are nouns.

Word	Noun	Adjective	Verb	Adverb
police work	Yes	No	No	No
roundup	Yes	No	No	No

As nouns, roundup is a hyponym of police work; that is, roundup is a word with a more specific, narrower meaning than police work:

Other hyponyms of police work include detecting, detection, detective work, sleuthing, forensics, surveillance.

police work (noun)	roundup (noun)
the investigation of criminal activities	the systematic gathering up of suspects by the police
	the activity of gathering livestock together so that they can be counted or branded or sold
	a summary list; as in e.g. "a news roundup"