Traitor in age of mistakes (6)
I believe the answer is:
errata
'mistakes' is the definition.
(an erratum is a mistake in a printed work)
'traitor in age' is the wordplay.
'traitor' becomes 'rat' (rat can mean a treacherous person).
'in' means one lot of letters goes inside another.
'age' becomes 'era' (both can mean a long time).
'rat' put inside 'era' is 'ERRATA'.
'of' is the link.
(Other definitions for errata that I've seen before include "List of printing mistakes" , "List of text corrections to be made in a publication" , "(Printing) errors" , "Mistakes (Latin)" , "Printing corrections" .)