Three-stroke heart radical on the left, the upright side form of 心. 愣 means to be stunned or blankly staring - a state of the mind. Anchors 愣 alongside 怕 to fear, 忆 to recall, 怒 to rage, 慌 to panic - chars naming what the heart-mind is doing.
Upper right is the net-eye component - historically a flattened 目 eye picturing eyes wide and fixed in a vacant stare. That blank-staring imagery is exactly what 愣 captures: someone frozen mid-thought with eyes locked but seeing nothing.
Lower right 方 supplies the sound - fāng shifting to lèng through an irregular old-Chinese reading that survives only in this char. Mostly phonetic; meaning rides on the heart radical plus the eye-net stare. A useful mnemonic: heart + blank eyes = frozen in a stare.
