This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
埻 combines 土 (earth) with 享, but the exact historical development and original meaning are uncertain.
The left side is earth 土, and the right side is 享. Without a clear meaning, picture a mound of earth shaped like the right component, but its purpose is unknown.
For シュン, imagine a soon-to-be-discovered meaning for this earth mound: soon -> シュン, and the mound waits patiently.