Snooty type returned top-quality little tree (6)
I believe the answer is:
bonsai
'little tree' is the definition.
(small ornamental tree)
'snooty type returned top-quality' is the wordplay.
'snooty type' becomes 'snob' (snobs are snooty or superior).
'returned' says the letters should be written in reverse.
'top quality' becomes 'ai' (resembles A1, informal term for top quality).
'snob' written backwards gives 'bons'.
'bons'+'ai'='BONSAI'
(Other definitions for bonsai that I've seen before include "Tree-dwarfing art" , "stunted growth" , "Art of dwarfing shrubs" , "Japanese craft of growing miniature trees" , "Little plants" .)