This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鐉 combines the metal radical 金 with the phonetic component 巽. The exact historical development and original meaning are uncertain.
The left side is metal 金, and the right side is 巽, a component associated with selection or arrangement. Without a clear meaning, picture a mysterious metal object being carefully chosen from a set.
For セン, imagine a sen coin (a small metal piece) being selected: sen -> セン, and the metal radical 金 reinforces the coin image.