Summary is almost exact (6)
I believe the answer is:
precis
'summary' is the definition.
(I know that precis is a type of summary)
'almost exact' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'exact' becomes 'precise' (associated in meaning).
'precise' with its final letter taken off is 'PRECIS'.
'is' is the link.
(Other definitions for precis that I've seen before include "Abstract; make summary (of text)" , "Digest - summary" , "Summary of the main points" , "Summary, short version" , "Summarize" .)