This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 靊 is uncertain. It visually combines 雨 (rain) with 豐 (abundant), but no clear etymological account is available.
Since no clear meaning is known, focus on the shape: rain 雨 pouring over an abundant harvest 豐, but treat the meaning as uncertain.
For フウ, imagine a strong wind (風, ふう) blowing rain over the abundant fields: 風 -> フウ, and the rain 雨 falls on the harvest 豐.