This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 恖 is uncertain. It visually contains 囟 (top of the head) and 心 (heart), but the original meaning and component relationship are unclear.
The top 囟 looks like a head, and the bottom 心 is a heart. Imagine thoughts rising from the heart to the head, but remember this kanji's meaning is uncertain.
For シ, picture a sheaf of thoughts tied together: sheaf -> シ, and the thoughts are held in the heart under the head.