Three short lines set a quiet image against something much heavier. A white deer appears in a park, a creature that looks pale, rare, almost unreal. Then the poem turns: the park is "troublesome / with the dust of war." Somewhere in this peaceful place, the memory or presence of war is still hanging in the air.
The word "troublesome" is an interesting choice. It's mild, almost understated, as if the speaker is struggling to name a feeling that is really much larger. The park should be calm, but it can't be, because the dust seems to settle on everything, including the deer. The whiteness of the animal may suggest innocence or fragility, and the dust threatens to stain it, though the poem only hints at this rather than saying so.
The mood is uneasy and hushed. The speaker doesn't shout or explain. They simply notice, and that restraint makes the unease linger. Peace here feels thin, and something unresolved is always close by.