A speaker lies awake on a night so hot and close that it feels unbearable. The title, "Muggy," sets the scene, and the four short lines pile on the discomfort without ever stating it outright, except in the third line: the night is "hot beyond bearing."
The images are strange and dreamlike. A swan "lodging in my clock" is hard to picture literally, but it might suggest a white, silent presence in the room, or the slow, heavy way time passes when you can't sleep. Calling the swan "elder brother to the air" makes it seem as thick and soft as the humid air itself. The last line turns into a plea. "Treacle of sleep" is a lovely phrase: sleep is imagined as something sweet, slow and sticky, the kind of relief the speaker longs to be given. The mood is drowsy, restless and a little prayerful, a small wish for the night to let go.