Outline is almost exact (6)
I believe the answer is:
precis
'outline' is the definition.
(I know that outline can be written as precis)
'almost exact' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'exact' becomes 'precise' (synonyms).
'precise' with its last letter taken off is 'PRECIS'.
'is' is the link.
(Other definitions for precis that I've seen before include "Prices for abbreviated version" , "Summarize" , "Synopsis, summary" , "Summary of the main points" , "Summary, short version" .)