Poplar or pine? (4)
I believe the answer is:
tree
I believe this clue is a double definition.
'poplar' is the first definition.
(I've seen this in another clue)
'pine?' is the second definition.
(pine is a kind of tree)
(Other definitions for tree that I've seen before include "Shoe __ or family __" , "Beech, for example" , "Large, woody perennial plant" , "eg Cedar" , "Large woody plant (4)" .)