Clarke runs a competitive line through each corner: he carries lots of rolling speed on corner entry and doesn't bind the car on corner exit. He places his car effectively in each corner, exploiting corner radius (consider, for example, his use of the apron at the exit of turns 7 and 9) and maximizing corner exit speed.
An early apex is not always unacceptable. When more grip is available in the second half of a corner (when, for example, a positive change in elevation exists in the second half of a corner) or when the turn has an increasing radius, an early apex is appropriate.
Clarke's lap is impressive, but for me his subtle, smooth inputs with the car's controls make his performance particularly noteworthy.