This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 宊 is uncertain. It visually combines 宀 (roof) and 犬 (dog), but whether this reflects the original formation is unclear.
With no clear meaning, picture a dog 犬 under a roof 宀: perhaps a guard dog inside a house, but the intended idea is unknown.
For トツ, imagine a dog under the roof suddenly dashing out: the sound of its paws is a quick 'totsu totsu' (トツ トツ), tying the reading to the visible dog component.