I think -- as an academic -- that academic means someone who belongs to Academe, an institution of higher learning. It has nothing to do with being intellectual, being a scholar, or indeed being knowledgeable or wise. It is a sociological distinction. It is worth pointing out that a scholar is much more highly regarded by academics than a "mere academic". There are very few scholars in universities -- people who are fully saturated in a subject to which they are themselves making substantial, worthy contributions. They are the exact equivalents of craftsmen in the arts and crafts. In 30 years in and out of universities in 4 countries I have met perhaps 10 scholars. They are revered -- the way Doc Watson or Pete Seeger are revered around here. They embody the subject, and why it is seen to be an integral expression of humanity at its best.
For a variety of reasons -- some mentioned -- it is very hard nowadays to be an academic, let alone s scholar in a traditional subject outside of university unless you are independently wealthy and very persistent. But it can be done. It is virtually impossible to do this in the sciences, simply because of access to equipment. It can be done: James Lovelock, the inventor of the Gaia Hypothesis, is an independent scientist.

yours, Peter T.