Solid Tory found on island (8)
I believe the answer is:
concrete
'solid' is the definition.
(I've seen this before)
'tory found on island' is the wordplay.
'tory' becomes 'con' (I've seen this before).
'found on' is a charade indicator (letters next to each other).
'island' becomes 'crete' (Crete is an example**).
'con'+'crete'='CONCRETE'
(Other definitions for concrete that I've seen before include "Definite; building material" , "Building material is not abstract" , "Strong, hard, building material" , "It's composed of sand, cement and water" , "Unsightly building material" .)