It might feature cases on an estate? (4,4)
I believe the answer is:
roof rack
'it might feature cases on an estate?' is the definition.
The definition suggests a singular noun which matches the answer.
This is all the clue.
(Other definitions for roof rack that I've seen before include "Carrier for holding luggage on top of a car" , "Framework for carrying things on car roof" , "Framework to carry luggage on top of car" , "Frame" , "Overhead luggage carrier" .)