What it means. What it takes.
Professionals are very good at the basics. The first thing a professional learns, the first thing they care about, is what the common pitfalls are, and how to avoid them. Professionals are very good at seeing where things could go wrong, and nipping potential problems in the bud.
Including in themselves.
Including when they don’t feel like it, or when the situation calls for a special effort. The professional is able to take themselves out of the equation when and if necessary. And if they aren’t able to, they know when to step down.
That’s what it means to be a professional. That’s what it takes to be professional.