Cat and ram loose on top of the road (6)
I believe the answer is:
tarmac
'top of the road' is the definition.
'cat and ram loose' is the wordplay.
'and' means one lot of letters go next to another (I've seen this in other clues).
'loose' is an anagram indicator (letters are loosened from their original positions).
'cat' after 'ram' is 'ramcat'.
'ramcat' with letters rearranged gives 'TARMAC'.
'on' acts as a link.
(Other definitions for tarmac that I've seen before include "Surface material of tar and broken stone" , "Road-surfacing substance" , "Topping" , "Airport runway(s)" , "Surfaced area for plane to land" .)