This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
櫕 combines 木 (tree/wood) with 賛, which likely contributes the sound. The exact historical development is uncertain.
The left side 木 suggests wood, and the right side 賛 is a common phonetic component. Without a clear meaning, picture a rare wooden object whose name sounds like サン.
For サン, imagine a wooden sun-shaped ornament: sun -> サン, and the wood radical 木 hints at the material.