This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鼦 combines 鼠 (rat/mouse) with 召, but the exact historical development and original meaning are uncertain. It may be a phono-semantic compound, but the details are unclear.
A mouse (鼠) beside a summoning shape (召) might suggest a creature called or named, but the meaning is unclear. Picture a mysterious mouse-like animal whose name is lost.
For チョウ, imagine a mouse (鼠) being summoned (召) by a distinctive invented name: Chou, the mouse. Chou -> チョウ.