In the end, ambassador will make you try again (6)
I believe the answer is:
rehear
'try again' is the definition.
('hear' can be a synonym for 'try' so perhaps 'rehear' is OK for 'try again')
'in the end ambassador' is the wordplay.
'in' is an insertion indicator.
'the end' becomes 'rear' (both can mean the back part of something).
'ambassador' becomes 'HE' (His or Her Excellency).
'rear' going around 'he' is 'REHEAR'.
'will make you' acts as a link.
(Other definitions for rehear that I've seen before include "Retry (a lawsuit)" , "Hold the trial again." , "Try again (in court)" , "be a sympathetic listener, not for the first time" .)