What was Jim Clark's driving style?
It was a Smooth Understeer driving style. This is why.
Jim Clark was known for having a fluid yet fast driving style. He would even slide the car around, four-wheel drifting but while being smooth with the inputs. This was clearly the fastest way to drive the 60s F1 cars as he won two World Championships with it.
It was noted that much like Alain Prost, he was able to use an understeery car to his advantage. It allowed him to carry more speed through corners, while being smooth. This saved his tyres, allowed him to have more consistent pace and looked after the unreliable 60s cars. This is not to mention his incredible talent of driving the car on the grip limit throughout the corner.