Boulevard divider (6)
I believe the answer is:
median
'boulevard divider' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for median that I've seen before include "Middle point or part" , "Middle value (statistics)" , "The middle of a series of values" , "Passing through the middle of Medina" , "In the middle; statistical value" .)