Summary that's accurate except for the last bit (6)
I believe the answer is:
precis
'summary' is the definition.
(precis is a kind of summary)
'accurate except for the last bit' is the wordplay.
'accurate' becomes 'precise' (synonyms).
'except for the last bit' means to remove the last letter.
'precise' with its last letter taken off is 'PRECIS'.
'that's' acts as a link.
(Other definitions for precis that I've seen before include "Prices for a summary" , "Abstract; make summary (of text)" , "Sketchy summary" , "Prices for abbreviated version" , "Summary, short version" .)