Row or rank (4)
I believe the answer is:
tier
This clue is a double definition.
'row' is the first definition.
(a tier is a row of things)
'rank' is the second definition.
(I know that tier is a type of rank)
(Other definitions for tier that I've seen before include "Row in theatre" , "Bank - row" , "Wedding cake layer" , "Level of a structure" , "One who secures" .)