Fertile tract in a desert (5)
I believe the answer is:
oasis
'fertile tract in a desert' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for oasis that I've seen before include "Area of calm amid hectic surroundings" , "Fertile spot in desert" , "Fertile tract in a desert" , "Place of peace" , "Q-and-A game" .)