I don't get clumping. I use an adequate quality pasta (De Cecco mostly), stir it when I put it in the water, and a few times after that, cooking to al dente. If I'm making a Caccio e Pepe or Carbonara I cook the spaghetti or (my preference) Buccatini I'm aiming for the minimum amount of liquid left, ideally just enough to put in the sauce. I use a frying pan so I can lay the noods out flat to minimise the water.
As I said I don't get clumping, it is absolutely possible to cook noods in minimal water without clumping because I do it so try switching some thing up if it's happening to you.
As I said I don't get clumping, it is absolutely possible to cook noods in minimal water without clumping because I do it so try switching some thing up if it's happening to you.