Walnut or chestnut (4)
I believe the answer is:
tree
I believe this is a double definition.
'walnut' is the first definition.
(thesaurus)
'chestnut' is the second definition.
(thesaurus)
(Other definitions for tree that I've seen before include "cross" , "Christmas decoration" , "Genealogist's graphic" , "Plane or pine, for example?" , "Diagram representing different relationships" .)