verb
Etymology: clamp (II)
transitive verb
1. : to clean (the deck of a boat) by spraying with water and swabbing down
2. : to impose (as a curfew, blackout, censorship) especially in a sudden, arbitrary, or violent manner
the police clamped down a deadline after which all slot machines were to disappear
intransitive verb
: to become suddenly or violently repressive, dire, or dictatorial
a military adventurer took over control of a free people and then clamped down — New Yorker
— usually used with on
the government was clamping down on Moslem activities — New York Times