Oldtime crossword puzzle fans know a puzzle may be made as difficult as desired by using (1) unusual or cryptic definitions or (2) strange or rare words.
The puzzle which follows sometimes employs either or both of these devices. But it is not just for the expert. It can also be solved by the persistent beginner.
Beaman, Ralph G.
Word Ways: Vol. 4
, Article 4.
Available at: https://digitalcommons.butler.edu/wordways/vol4/iss4/4