This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
槮 combines 木 (tree) with 參, which likely contributes a phonetic element. The exact historical development is uncertain.
The left side is a tree 木, and the right side is 參. Without a clear meaning, picture a rare tree with a complex, three-part shape like 參.
For シン, imagine a thin, rare tree: thin -> シン, and the tree 木 stands beside the complex 參.