1 [always + adverb/preposition]
to put or hold something in a position so that it cannot move:
She clamped her hands over her ears.
Creed opened his mouth to speak, then clamped it shut.
to put limits on what someone is allowed to do:
The President clamped sanctions on the island after the bomb attack.
3 [always + adverb/preposition]
to hold two things together, using a clamp:
Clamp the two parts together until the glue dries.
4 also wheel-clamp [usually passive] British English
to put a clamp on the wheel of a car so that the car cannot be driven away. This is usually done because the car is illegally parked [= boot American English]
He returned, only to discover his car had been clamped.
clamp downphrasal verb
clamp down on
The police are clamping down on drink-driving offenders.