Solid building material (8)

I believe the answer is:

concrete

I believe this clue is a double definition.

'solid' is the first definition.
(similar in meaning)

'building material' is the second definition.
(concrete is a kind of building material)

(Other definitions for concrete that I've seen before include "factual type of evidence?" , "Substantial, real" , "Definite; building material" , "Unsightly building material" , "Real, not abstract" .)

I've seen this clue in The Sun and the Irish Times (Simplex).

Want a hint initially instead of a full solution? Install my app