Some up in elm tree (4)
I believe the answer is:
pine
'tree' is the definition.
(pine is a kind of tree)
'some up in elm' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'PINE' is hidden within 'up in elm'.
(Other definitions for pine that I've seen before include "Mope; tree" , "Coniferous tree" , "Thirst" , "Fir tree; languish" , "Conifer grown for wood" .)