This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
箺 combines 竹 (bamboo) with 春 (spring). The exact historical development is uncertain, but it likely referred to a type of bamboo or a bamboo-related object.
Bamboo 竹 in spring 春 suggests new bamboo shoots, but the kanji's meaning is unclear.
For シュン, imagine a bamboo shoot in spring: the spring season 春 (しゅん) cues the reading シュン.