Tree in a tray (6)
I believe the answer is:
bonsai
'tree in a tray' 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 "Japanese art of growing dwarf plants" , "Tree dwarfing art" , "specimen with restricted roots?" , "Potted tree or shrub artificially prevented from reaching normal size" , "Dwarf tree cultivation" .)