Level with the tree (5)
I believe the answer is:
plane
I believe this is a double definition.
'level' is the first definition.
(plane is a kind of level)
'the tree' is the second definition.
(plane is a type of tree)
'with' is the link.
(Other definitions for plane that I've seen before include "that soars into the sky" , "This flier" , "Aircraft - level surface - carpenter's tool" , "Smooth" , "Form of transport" .)