This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
槯 is a phono-semantic compound with 木 (tree) on the left and 崔 on the right, which likely contributes the sound. The exact historical meaning is uncertain.
A tree 木 beside 崔, a component associated with high mountains. Picture a tall tree on a mountain, but its exact meaning remains unclear.
For サイ, imagine a sighing tree on a mountain: sigh -> サイ, though the tree's purpose is uncertain.