What's normal for street - and a road (8)
I believe the answer is:
standard
'what's normal' is the definition.
('standard' is associated in meaning with 'normal')
'street and a road' is the wordplay.
'street' becomes 'st'.
'road' becomes 'rd' (abbreviation).
'st'+'and'+'a'+'rd'='STANDARD'
'for' is the link.
(Other definitions for standard that I've seen before include "Ordinary Level?" , "Accepted model - flag" , "Normal quality" , "Basic criterion" , "Classic" .)