Row, level (4)
I believe the answer is:
tier
I believe this clue is a double definition.
'row' is the first definition.
(a tier is a row of things)
'level' is the second definition.
(I know that level can be written as tier)
(Other definitions for tier that I've seen before include "Layer, rank" , "Rite (anag.)" , "Rite for a rank" , "One of two or more rows" , "Row, level" .)