Wide thoroughfare (6)
I believe the answer is:
avenue
'wide thoroughfare' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for avenue that I've seen before include "Wide and handsome street" , "Wide street or way of approaching" , "A broad wide street" , "A broad thoroughfare as in New York" , "Road lined with trees" .)