Grass radical on top - the top-cap form of 艸. It indexes 蔑 in the plant section, though here the connection is graphic rather than botanical: the three strokes once represented eyebrows in the oracle-bone form of the character.
Middle 罒 is the horizontal form of 目 eye. The original picture showed an eye with downcast lashes - a contemptuous sidelong glance. This is the semantic core of 蔑 'to look down on; to scorn'.
Bottom 戍 pictures a soldier with a spear standing guard. Combined with the sideways eye above, the full graph evokes an armed figure casting a withering glare - sharpening 'scorn' into something hostile and dismissive.
