House in Home Counties beside busy road (4)
I believe the answer is:
semi
'house' is the definition.
(I've seen this before)
'home counties beside busy road' is the wordplay.
'home counties' becomes 'se'.
'beside' is a charade indicator (letters next to each other) (I've seen this in other clues).
'busy road' becomes 'mi' (resembles M1, English motorway).
'se'+'mi'='SEMI'
'in' is the link.
(Other definitions for semi that I've seen before include "Connected house" , "Property attached to another" , "Prefix meaning half or partly" , "Prefix meaning half (4)" , "One of two houses with a common wall" .)