Cf. "What Is Poetry?"
Philosophy is an art. It is the art of writing down how (not what) you think.
Philosophy makes you think better. It makes you better able to think, better at thinking.
Concepts are how (not what) we think. Philosophy makes your concepts more precise.
Precision in thinking is clarity. Philosophy is clear.
Philosophy is conceptual notation, the art of writing concepts down.
Philosophy makes you think better by getting you to notice your concepts.