Art of growing dwarfed trees (6)
I believe the answer is:
bonsai
'art of growing dwarfed trees' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bonsai that I've seen before include "Dwarfed ornamental tree or shrub" , "Very little tree" , "small growth" , "Japanese craft of growing miniature trees" , "Mini-tree growing" .)