This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鍽 combines 金 (metal) with 扁, which likely contributes the sound. The exact historical development is uncertain.
The left side is metal 金, and the right side is 扁. Without a clear meaning, picture an unknown metal object with a flat, board-like shape suggested by 扁.
For ヘン, imagine a hen pecking at a flat metal piece: hen -> ヘン, and the metal 金 is shaped like 扁.