The phrase "to crack down on" means to take strict measures or enforce laws and rules more strictly in order to prevent something from happening, or to punish those who are doing it. Full definition
But should the shit ever hit the fan and governments start cracking down on cryptocurrencies, these heavily centralized altcoins will be the first to go. (ccinews.net)
The shadow minister for home affairs has promised that a Conservative government would preserve the right for people to legitimately possess firearms while cracking down on illegal gun culture. (politics.co.uk)
About half of the cost is due to increased consumption of natural gas that will be the side - effect of cracking down on coal. (macleans.ca)