The phrase "clamping down" can be described using a variety of synonyms, each with its own specific connotation. One possible synonym is "cracking down," which implies a strong, forceful response to a situation in order to maintain control. Another synonym could be "tightening up," which suggests a more gradual, systematic approach to enforcing rules or regulations. "Policing" is also a possible synonym, which has more of a connotation of monitoring and regulating behavior. Other synonyms for "clamping down" may include "enforcing," "restricting," "constraining," "curtailing," "suppressing," or "crushing." The chosen synonym will depend on the specific context in which the phrase is being used.