Doesn't there have to be a bit of 'altruistic' in the definition?
And a code of ethics?
So take nursing.
When I first worked for the NHS nurses could be
SRN / RGN /RGHN
SEN
Auxiliary
None of them took degrees (that was just coming in)
The 'State Registered' or 'Registered - type of nurse' did three years training, possibly longer if they had done a pre nursing course.
SEN - did a 2 year course, they worked as nurses but could not progress to higher levels such as sister, senior sister etc.
Auxiliary - had no or very little training
RGN and other 'registered' nurses have at least a diploma but under the latest training they have to take a degree.
You no longer get SEN nurses, some converted as part of various upgrade courses, others worked until retirement. You might get the odd one still around.
Auxiliary also no longer exists, HCA have taken their place and they take level 2 and level 3 training courses.
So if you go for:
Highly trained
Professional body that you need to stay 'in good standing' with or you cannot work
Code of ethics
Then nursing is a Profession, but in the past it wasn't, or wasn't entirely.
Nurses now work in much wider roles than they used to, they are involved in research and publish work in journals, not things nurses training in the 1960s / 1970s would do.