One with property left over an unhappy experience (9)
I believe the answer is:
landowner
'one with property' is the definition.
'left over an unhappy experience' is the wordplay.
'left' becomes 'l' (common abbreviation).
'over' is a charade indicator (letters next to each other) (in a down clue, some letters go over others).
'unhappy experience' becomes 'downer' (a downer is a depressing experience).
'l'+'an'+'downer'='LANDOWNER'
(Other definitions for landowner that I've seen before include "Owner of an area" , "One may have lots of grass" , "Man of means" , "Squire, perhaps" , "Laird" .)