This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鉠 combines 金 (metal) with 央, which likely contributes the sound. The exact historical meaning is uncertain.
The left side is metal 金, and the right side is 央. Without a clear meaning, picture an unknown metal object with a central 央 shape.
For エイ, imagine an ancient metal tool called an 'A' (エイ) that has a central 央 mark.