This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 惉 is uncertain. It visually contains 沾 and 心, but the original semantic and phonetic roles are unclear.
The top 沾 suggests moisture or soaking, and the bottom 心 is heart. Imagine a heart soaked in uncertainty, its meaning unclear.
For セン, picture a heart (心) soaked in a sen (千) tiny droplets: 千 -> セン, and the heart is drenched in confusion.