段

Right indexing lance radical 殳 (Kangxi #79) - a hand holding a long-handled weapon. Carries the action: striking the cliff to break off pieces. Same radical anchors 投 (throw), 殴 (beat), 毁 (destroy), 段 - all violent or forceful actions performed with a stick or hand-held implement.

Left 5 strokes - the hint marks this slot unknown because it's an Ext-A glyph with no clean modern reading. Historically these strokes depict a section of cliff being struck off: a vertical face with horizontal layering and a downward-pointing chip. The picture explains 段's core sense of 'a piece broken off,' from which came 'section, paragraph, period of time.'