This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
棭 combines 木 (tree) with 夜 (night), but the exact historical development and original meaning are uncertain.
The left side is a tree 木, and the right side is night 夜. Picture a tree at night whose identity is unclear in the dark, matching the uncertain meaning.
For エキ, imagine a mysterious tree at night that gives off an eerie liquid (液, エキ) glow: エキ from 液 cues the reading, and the tree 木 ties it to the kanji.