This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
炗 is an ancient form of 光, combining 火 (fire) with a person-like element above, representing light from a fire held by a person. The exact historical development is uncertain.
The top 廿 looks like a person holding something, and the bottom 火 is fire. Picture a person holding a torch, producing light.
For コウ, imagine a person holding a glowing coal: coal -> コウ, and the fire lights the way.