Flog wood (5)
I believe the answer is:
birch
I believe this is a double definition.
'flog' is the first definition.
(birching is a kind of flogging)
'wood' is the second definition.
(I've seen this before)
(Other definitions for birch that I've seen before include "Wood" , "Tree, maybe silver" , "Flogging rod" , "Tree bearing catkins" , "to beat the rest?" .)