Rustic cultivated tree (6)
I believe the answer is:
citrus
'tree' is the definition.
(citrus is a kind of tree)
'rustic cultivated' is the wordplay.
'cultivated' is an anagram indicator.
'rustic' is an anagram of 'CITRUS'.
(Other definitions for citrus that I've seen before include "Lemons, limes, oranges etc." , "Eg, a lime tree" , "Type of tree bearing acidic fruit" , "sort of fruit tree" , "Fruit tree genus" .)