Five short lines, one unfinished sentence, and a confession that sounds almost casual: the speaker wishes they could get rid of their own imagination. The reason is the scene it keeps producing, in which "we set the world alight / With just a few cigarettes / And that night." The central idea is that imagination is not always a gift. When it shows you something vivid and shared and out of reach, it becomes a source of ache, and the speaker would rather be without it.
The first line sets the tone. "Do away with" is the language of getting rid of a nuisance, flat and practical, as if imagination were a piece of clutter. The second line makes it more personal: "this imagination of mine." The word "this" points at the thing as though it were sitting in the room, and "of mine" admits ownership while hinting at helplessness. You own it, but you can't switch it off. There is also a neat irony in the title. "Fantasy" promises a daydream, yet the poem opens by rejecting daydreams, and it is itself built out of the imagination it wants to remove. The wish is made with the very faculty it wishes away.
The imagery is where the poem plays its best trick. "Set the world alight" is an everyday idiom for making a huge impact, and the poem makes it literal by attaching cigarettes, which need a flame. The scale is deliberately absurd: the whole world, and "just a few cigarettes." That "just" deflates the grandeur and makes the line tender and a little funny. The suggestion, and it is only an inference from the text, is that the fire comes from the feeling between two people, not from the means. "Alight" also means lit up, not burned down, so the world is illuminated rather than destroyed. A cigarette, though, is an ember that burns steadily down to ash, which quietly suggests a brightness that cannot last.
Notice the small words around the images. Imagination is a place, "where" things happen, and the only company in it is "we." The poem never says who that is, so the reader supplies the person. "That night" is just as unspecific. The word "that" points at one particular night, which might be remembered or might be invented. The title leans toward invention, but the poem will not settle the question, and that uncertainty is part of its ache.
The form does a lot with very little. There is no regular rhythm and no rhyme scheme, but "alight" and "night" chime across the third and fifth lines, a faint echo that closes the poem on opposites, light and dark, the two things a lit cigarette in the dark brings together. The lines also shrink. The second, carrying the long word "imagination," stretches to about nine syllables, and by the end the poem has narrowed to a three-syllable fragment. That last line has no verb and no firm ending, and it begins with "And," as if the speaker were adding one more item to a list and then lost the thread. The night comes last in the list and gets the fewest words, which makes it sound like the most important thing and the hardest to say. The poem fades the way smoke does.
What makes it significant is how much feeling it fits into so little space. The vocabulary is plain, there is one borrowed idiom, and nothing is explained. Yet we get desire, regret, intimacy and a kind of self-mockery, all held in the gap between the huge claim ("the world") and the tiny means ("a few cigarettes"). It also refuses to resolve. The speaker does not manage to stop imagining, and the poem ends mid-thought, still inside the scene it says it wants to leave. For a reader, that is the real point: a wish to forget is itself a way of remembering, and the poem proves it by being written at all.