Plant embedded in stone thoroughfare (6)
I believe the answer is:
street
'thoroughfare' is the definition.
(street is a kind of thoroughfare)
'plant embedded in stone' is the wordplay.
'plant' becomes 'tree'.
'embedded in' indicates putting letters inside (I've seen this in other clues).
'stone' becomes 'st' (abbreviation).
'tree' put into 'st' is 'STREET'.
(Other definitions for street that I've seen before include "Part of motorist's route" , "Town road" , "See 14" , "Tester (anag.)" , "A thoroughfare or public road" .)