Mistakes made by a deserter in time (6)
I believe the answer is:
errata
'mistakes' is the definition.
(an erratum is a mistake in a printed work)
'a deserter in time' is the wordplay.
'a deserter' becomes 'rat' (both can mean a traitor).
'in' means one lot of letters goes inside another.
'time' becomes 'era' (an era is a period of time).
'rat' put into 'era' is 'ERRATA'.
'made by' is the link.
(Other definitions for errata that I've seen before include "Mistakes in printed material" , "List of printed mistakes" , "Printing corrections" , "Misprints in a book" , "Boobs in a book" .)