Let\'s say I have a class Employee
with a huge amount of fields. And I have a lot of actions related to db with it like CRUD, filter etc.
In MVC patter
I think that normaly will be if the Model contains only the definition of Model classes with geters and setters and all Business Logic in separate classes - maybe separate layer, you can call them EmployeeActions or maybe better EmployeeManager in such way we keep separated logic from definition. But this is only required when you have complex application. Sometimes introducing any additional layers may add unwanted complexity to the code.
I think a good answer is: https://softwareengineering.stackexchange.com/a/165470