Tidy growth in forestry (6)
I believe the answer is:
spruce
'tidy' is the definition.
(similar in meaning)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for spruce that I've seen before include "thing for fairy to be on top of?" , "wood" , "Smart, trim" , "Coniferous tree" , "Neat - evergreen" .)