Boy in black tie departs, abandoned (10)
I believe the answer is:
jettisoned
'abandoned' is the definition.
(thesaurus)
'boy in black tie departs' is the wordplay.
'boy' becomes 'son' (synonyms).
'in' indicates putting letters inside.
'black' becomes 'jet' (similar in meaning).
'departs' becomes 'd' (common abbreviation e.g. train timetables).
'jet'+'tie'='jettie'
'son' going inside 'jettie' is 'jettisone'.
'jettisone'+'d'='JETTISONED'
(Other definitions for jettisoned that I've seen before include "Thrown away" , "Ditched" , "dumped" , "Threw away" , "Thrown overboard" .)