This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 鏅 is uncertain. It combines 金 (metal) with 脩, but the original semantic and phonetic roles are unclear.
The kanji has metal 金 on the left and a complex right side. Without a clear meaning, picture a mysterious metal object being forged and refined.
For シュウ, imagine a shoe made of metal: shoe -> シュウ, and the metal shoe is being forged on the right side.