limit vs clamp down

limit is a noun but clamp down is not a noun.

Word	Noun	Adjective	Verb	Adverb
limit	Yes	No	Yes	No
clamp down	No	No	Yes	No

As verbs, clamp down is a hyponym of limit; that is, clamp down is a word with a more specific, narrower meaning than limit:

limit (noun)	clamp down (noun)
the greatest possible degree of something
the boundary of a specific area
as far as something can go
the greatest amount of something that is possible or allowed
the mathematical value toward which a function goes as the independent variable approaches infinity
final or latest limiting point

limit (verb)	clamp down (verb)
restrict or confine within limits	repress or suppress (something regarded as undesirable)
place limits on (extent or amount or access)
decide upon or fix definitely