This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
綧 combines 糸 (thread) with 享, which likely contributes the sound. The exact historical development is uncertain.
The left side is thread 糸, and the right side is 享. Without a clear meaning, picture tangled threads that need to be sorted out.
For シュン, imagine a shun (avoid) tangled threads: shun -> シュン, and you quickly move past the messy 綧.