With today's age of texting and truncating of words, the English language is changing at breakneck speeds. But here is the accepted definition of professional. Note that it also encompasses anything related to one's profession:
b : engaged in one of the learned professions
c (1) : characterized by or conforming to the technical or ethical standards of a profession (2) : exhibiting a courteous, conscientious, and generally businesslike manner in the workplace
bolded meaning that Canon is referring to. And what your meaning is:
b : having a particular profession as a permanent career a professional soldier
c : engaged in by persons receiving financial return professional football
So, both equally valid definitions of the word professional.