Well-equipped place for caravans en route (5)
I believe the answer is:
'well' is the definition.
(source of water)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for oasis that I've seen before include "Green area in desert" , "beauty spot" , "Fertile patch in a desert" , "Place of refreshment" , "Fertile spot in desert" .)