Chosen tart with a soft topping (9)
I believe the answer is:
appointed
'chosen' is the definition.
(thesaurus)
'tart with a soft topping' is the wordplay.
'tart' becomes 'pointed' (both can mean sarcastic or acerbic).
'with' is a charade indicator (letters next to each other).
'soft' becomes 'p' (musical abbreviation for 'piano').
'topping' is a charade indicator (letters next to each other).
'a' next to 'p' is 'ap'.
'pointed' put after 'ap' is 'APPOINTED'.
(Other definitions for appointed that I've seen before include "Given a job" , "Assigned to a position" , "Given the situation" , "Taken on" , "Selected for a job" .)