Scour brushwood (5)
I believe the answer is:
scrub
I believe this clue is a double definition.
'scour' is the first definition.
('scrub' can be a synonym of 'scour')
'brushwood' is the second definition.
(thesaurus)
(Other definitions for scrub that I've seen before include "Curbs (anag.)" , "Rub hard with a brush" , "Powerful wash" , "plants" , "Vegetation consisting of stunted trees or bushes" .)