Abandon last course without son (6)
I believe the answer is:
desert
'abandon' is the definition.
(synonyms)
'last course without son' is the wordplay.
'last course' becomes 'dessert' (I've seen this before).
'without' is a deletion indicator.
'son' becomes 's' (genealogical abbreviation for son).
'dessert' with 's' taken out is 'DESERT'.
(Other definitions for desert that I've seen before include "Abandon in barren terrain" , "Abandon in arid area" , "Hot dry area" , "Waterless area of land" , "Defect, forsake" .)