Birch or willow (4)
I believe the answer is:
tree
I believe this clue is a double definition.
'birch' is the first definition.
(I've seen this before)
'willow' is the second definition.
(thesaurus)
(Other definitions for tree that I've seen before include "Oak, for example" , "eg Rowan" , "Large shrub; family line" , "Christmas decoration" , "Elm, perhaps" .)