This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蚹 combines 虫 (insect) with 付, which likely provides the sound. The exact historical development is uncertain.
The insect radical 虫 suggests a bug-related meaning, but without a clear definition, picture a mysterious insect clinging to a surface like 付 (attach).
For フ, imagine a fly (フ) buzzing around the insect radical 虫: the sound of a fly cues フ.