Raw materials from forests (4)
I believe the answer is:
ores
'raw materials' is the definition.
(I've seen this in another clue)
'from forests' is the wordplay.
'from' says the answer is hidden in the clue.
'ORES' can be found hidden inside 'forests'.
(Other definitions for ores that I've seen before include "Mined minerals" , "Sources of metal" , "Rocks or minerals containing metals" , "Mineral deposits" , "Metal-bearing minerals" .)