Left hand radical, the side-form of 手. The indexing radical, marking 描 as a hand-action verb: to trace, sketch, depict with a brush. Same radical groups it with 拓 (rub a copy), 抄 (copy out), 写 (write). Anything done with a deliberate brush stroke.
Right 苗 supplies the sound directly, miáo matches the whole reading with no drift. 苗 itself shows 艹 grass over 田 field, a young sprout. Same phonetic feeds 瞄 (take aim), 喵 (meow), 锚 (anchor), 渺 (vague), all in the miáo family.
