Material in half a brick (6)
I believe the answer is:
fabric
'material' is the definition.
(I know that material can be written as fabric)
'in half a brick' is the wordplay.
'in' indicates the answer is hidden within the clue.
'FABRIC' is hidden in the letters of 'half a brick'.
(Other definitions for fabric that I've seen before include "stuff" , "Manufactured cloth" , "'Cloth, textile (6)'" , "Woven or knitted material" , "Woven textile" .)