Lumber or timber (4)
I believe the answer is:
wood
This clue is a double definition.
'lumber' is the first definition.
(I've seen this in another clue)
'timber' is the second definition.
(I've seen this before)
(Other definitions for wood that I've seen before include "Grove" , "Golf club - tree material" , "Kind of musical instrument" , "Section of orchestra" , "Lots of trees" .)