Responsibility about betting getting ambassador to swear (9)
I believe the answer is:
blaspheme
'to swear' is the definition.
(synonyms)
'responsibility about betting getting ambassador' is the wordplay.
'responsibility' becomes 'blame' (I've seen this in another clue).
'about' means one lot of letters goes inside another.
'betting' becomes 'sp'.
'getting' is a charade indicator (letters next to each other).
'ambassador' becomes 'HE' (His or Her Excellency).
'sp'+'he'='sphe'
'blame' placed around 'sphe' is 'BLASPHEME'.
(Other definitions for blaspheme that I've seen before include "Say irreverent things about God" , "Utter obscenities or profanities" , "Speak irreverently about God" , "Curse, profane" , "Swear" .)