Flag seen in street and a road (8)
I believe the answer is:
standard
'flag' is the definition.
(I know that standard is a type of flag)
'street and a road' is the wordplay.
'street' becomes 'st' (abbreviation).
'road' becomes 'rd' (abbreviation).
'st'+'and'+'a'+'rd'='STANDARD'
'seen in' is the link.
(Other definitions for standard that I've seen before include "Criterion, touchstone" , "Established model - flag" , "Accepted model - flag" , "Principle" , "Possible 1930s song" .)