Seating tier (3)
I believe the answer is:
row
'seating tier' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for row that I've seen before include "Propel a boat with the tier" , "Series" , "Line; squabble" , "Informal quarrel or a straight line" , "Barney - rank" .)