A restrictive action
Any kind of clamp implies restraint – to dream of one indicates we are being prevented from making progress in our spiritual aims.
Psychological / emotional perspective: To find ourselves using a clamp such as a woodworking tool suggests having to make an extra effort to hold a situation stable.
Material aspects: A car being clamped in dreams suggests a deliberate bar to movement. This may be because a particular task has taken too long, because authority has stepped in or because we have not paid enough attention to detail.
Dreams of a clamp represent being closed up emotionally, your lips are sealed and your secrets are safe. Perhaps you are feeling shut down, protected and afraid of exposure.