Built a villa in Serbia, against the odds, and it's vacant (9)
I believe the answer is:
available
'vacant' is the definition.
(thesaurus)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for available that I've seen before include "Not occupied, free" , "To hand" , "Free; within reach" , "Able to be used, free" , "handy" .)