Forest contains raw materials (4)
'raw materials' is the definition.
'ores' can be an answer for 'materials' (ore is a kind of material). I'm not sure about the 'raw' bit.
'forest contains' is the wordplay.
'contains' indicates the answer is hidden within the clue.
'ORES' is hidden in the letters of 'forest'.
Can you help me to learn more?
(Other definitions for ores that I've seen before include "Bauxite, haematite etc", "Mined minerals", "Mineral deposits", "Metal-bearing minerals", "Sources of metal".)