The poem sets a quiet morning on open moorland against the idea of a town. The opening line is calm and spacious, but the next lines turn strange: the town is "in possession / of no place." It owns nothing here, even though it has "enclosed" the land. The grammar is a little twisted, which suits the idea. Ownership and fencing don't quite make sense out on the moor.
The last lines, "could not stay / the night," suggest that the town's hold is only temporary. Human settlement can claim and mark off the land by day, but it cannot last through the dark, when the moor seems to take itself back. Judging by the imagery, the speaker isn't angry or alarmed. The tone feels watchful and a little amused, even humbled, as if observing how small human claims are in a wide landscape. The mood is still, slightly eerie, and open, with plenty of silence left around the few words, much like the moor itself.