Possibly major row (4)
I believe the answer is:
rank
This clue is a double definition.
'possibly major' is the first definition.
(I know that major is a military rank)
'row' is the second definition.
(as in a taxi rank)
(Other definitions for rank that I've seen before include "Grade; foul" , "Fetid" , "stink in > class" , "Downright" , "Level; smelling bad" .)