Left indexing radical - pinching is a hand action, specifically using thumb and forefinger pressed together. The hand-radical heads all manual gripping verbs: 抓 (grasp), 捏 (squeeze), 摸 (touch), 揪 (tug). Almost mandatory for grip-related actions.
Right 臽 supplies the sound (xiàn → qiā, drifted but in the same Old Chinese root) with a faint semantic kick: pinching traps flesh between two fingers, just as 臽 depicts a person fallen into a pit. Same phonetic in 陷 (sink), 馅 (filling).
