The speaker describes himself as a sore, weary child stranded "at the end of the earth," a place that feels remote and forgotten. The word "achy" is simple and childlike, but it hints at a tiredness that goes beyond the body, a general ache of being left out or overlooked.
The middle of the poem turns oddly playful. Picking Sunkist oranges from the top of a billboard is an impossible, almost comic image, since the fruit is only an advertisement. The speaker shrugs it off: it's "largely immaterial." Whether he reaches for something bright and unreal or not, nothing changes. In the last lines he admits what he actually does, which is wait for whatever the world lets fall, "hat in hand," like a beggar or a humble petitioner. The mood is quietly wry and resigned. There's a little humor in the billboard image, but underneath it sits a lonely sense of dependence and small expectations.