Tree that goes high up into the sky (5)
I believe the answer is:
plane
This clue is a double definition.
'tree' is the first definition.
(plane is a type of tree)
'that goes high up into the sky' is the second definition.
(Other definitions for plane that I've seen before include "Tree - figure - aircraft" , "Smooth" , "What imitates bird" , "Form of transport" , "Smoother" .)