This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
葥 combines the plant radical 艹 with 前, which likely contributes sound. The exact historical development is uncertain.
The plant top 艹 over 前 suggests a plant whose name sounds like セン. Without a clear meaning, picture a mysterious plant called 'sen' growing ahead.
For セン, imagine a centipede crawling over the plant 葥: cent -> セン, and the plant's name sounds like 'sen'.