I got a couple cats from the shelter a long time ago. One of the coolest things, they trained them to allow claw trimming and taught us how to keep it going.

Super high-value treats, do this over the course of weeks or months, whatever it takes. a treat to touch a paw -> a treat to hold a paw -> a treat to touch a bean -> a treat to inspect a nail -> a treat to touch a tool to a nail -> a treat to nip the tip -> a treat to nip 2 tips -> yada yada

one step at a time, most will eventually give.