Not binders, but seating arrangements (5)
I believe the answer is:
tiers
'arrangements' is the definition.
(tier is a kind of arrangement)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for tiers that I've seen before include "drawers?" , "I rest in layers" , "Layers, levels" , "Row upon row" , "Layers, strata" .)