Well,
kanjin is a na-adjective so the
na is just the
na that normally follows it. The
no then nominalises
kanjin-na. Overall I think it works like the "one" in "the most important one is ...", where "one" usually means "of these", referring to a list of some kind.
For example, you could say "cookery requires many skills" (or maybe you could ask "what skils are required for cookery?") and follow up with:-
kanjin na no wa <cookery-skill>
da.
Or you might say "cookery requires patience, dedication and a bag of nails" but then go on to point out that the most important thing is not one of those but something else:-
demo kanjin na no wa <additional-cookery-skill>
da.
マイケル
