Hand part, or a tree (4)
I believe the answer is:
palm
This clue is a double definition.
'hand part' is the first definition.
('palm' is part of 'hand')
'a tree' is the second definition.
(palm tree is a kind of tree)
(Other definitions for palm that I've seen before include "Obscure" , "Conceal in the hand" , "Underside of hand" , "Date-tree" , "prize" .)