Middle of roadbed relaid in brick (5)
I believe the answer is:
adobe
'brick' is the definition.
(adobe is a kind of brick)
'middle of roadbed relaid' is the wordplay.
'middle of' indicates the central letters.
'relaid' indicates anagramming the letters (letters laid again).
The centre of 'roadbed' is 'oadbe'.
'oadbe' with letters rearranged gives 'ADOBE'.
'in' acts as a link.
(Other definitions for adobe that I've seen before include "Sun-dried brick clay" , "Clay for mud bricks" , "house" , "Mexican mud and straw brick, and the hut made of it" , "Building material of clay and straw dried in the sun" .)