Trim; a tree (6)
I believe the answer is:
spruce
I believe this clue is a double definition.
'trim' is the first definition.
(synonyms)
'a tree' is the second definition.
(I know that Spruce is a type of Pinaceae)
(Other definitions for spruce that I've seen before include "Smart, trim" , "Natty as a tree" , "Evergreen pyramid-shaped tree" , "Neat and tidy like tree" , "Neat and dapper tree" .)