upper-story door or window
闒 refers to a door or window on an upper story of a building. The meaning is narrow and architectural, with no clear broader conceptual center.
闒 is a phono-semantic compound with 門 (gate, door) and a phonetic element that is now obscure. The exact historical development of the inner component is uncertain.
The 門 enclosure suggests a gate or door. Imagine a tall gate with a window above it, like an upper-story opening in an old building.
For トウ, picture a tall tower with an upper-story window: tower -> トウ, and the window is high up in the gate-like structure.