Thirteen words, three lines, and a speaker bold enough to address a clock as if it were a strict employer who might be talked round. That is the whole situation of "Slacker": someone hemmed in by the day's schedule, quietly pleading for time to loosen its grip. The poem never shows the speaker slacking. It doesn't need to, because the title has already confessed on the speaker's behalf.
The opening, "O busy clock", borrows the grand "O" of odes and prayers and aims it at a household object. The mismatch is funny, but the affection in it is real. "Busy" is the key word. A clock isn't busy the way people are, yet it never stops ticking, and by giving it a human fault the speaker turns it into a colleague who is always hurrying past with somewhere to be. That makes the title click. If the clock is the busy one, the speaker is, by contrast, the slacker, and the poem treats the word less as an insult than as a position it is willing to hold.
The middle line is the trickiest: "the hour I want could finish". Look at what is not there. The speaker doesn't say "need" or "ought", only "want", so desire is set against duty. The speaker doesn't command either. "Could" is a conditional, a shrug of a verb, and even the protest is too relaxed to raise its voice. There is no punctuation, so the grammar can tilt two ways. The wanted hour might be the one that arrives and brings the busy stretch to an end. Or the line might simply wish for an hour allowed to run its course without being hurried along. The poem doesn't choose, and the uncertainty suits a speaker too unhurried to tidy up their own sentence. "Finish" is also an odd verb here, because we usually ask for time to be given or to begin. The speaker asks for an ending, as if the way to gain time were to let the clock's work run out.
Then comes "and let us be", the line where the poem turns. The singular "I" of the second line widens into "us", and the poem never says who that is. It might be the speaker and a companion, the speaker and the hour, or everyone who has ever watched a clock. The phrase also works twice. On the surface it means "leave us alone", but "be" is also the plainest verb of existence, standing with no object and no task. The poem has moved from "busy", a word full of doing, to "be", a word that does nothing at all.
The shape carries the same movement. The lines run short, long, short, about four syllables, then seven or eight (depending on how you say "hour"), then four. The longest line sits in the middle like the hour it describes, stretched out, before the ending settles into four small monosyllables. "And let us be" almost sinks, like an exhale. There is no rhyme and no capital letter apart from "O" and "I". Without them, the lines drift rather than march. The first line can be heard as a tick, "O BUS-y CLOCK", but the poem slips out of that beat as it goes, as though it were declining to keep time. Even the sounds make the point: the hard "k" of "clock" gives way to the soft "sh" of "finish" and finally to the open vowel of "be".
What makes the poem worth reading is how much argument it fits into so little room. Calling someone a slacker is usually an accusation, but here it is a title worn lightly, and the poem makes a quiet case that wanting unscheduled time is a human wish rather than a moral failing. Its brevity is part of the case. A poem this short takes almost none of the reader's time, so it practises what it asks for. It talks to the clock for a few seconds, then stops and lets the silence after "be" do the rest.