The poem sets lightness against weight. In the first lines the speaker imagines being a kite, something airborne and free enough to be "impertinent" toward "the weight of numbers." Numbers here might suggest counting, measuring, accounting, all the things that pin a person down. A kite can cheekily ignore them because it floats above.
Then the poem drops. Cellars are the opposite of sky: low, dark, heavy. The image of night "spoiling" there makes it feel like something stored too long and going bad. The mood turns uneasy.
The last stanza is the most puzzling. The speaker fears "the atelier," a workshop where things are made, "if we must have hands." Judging by the imagery, hands may stand for work, craft, or the obligation to make and produce, and the speaker seems wary of that. A kite has no hands, after all. The title, "Dilettante," supports this reading: someone who dabbles lightly, unwilling to be tied to serious labor. The feeling is half playful, half anxious.