Page that is about traitor and main criminal (6)
I believe the answer is:
pirate
'main criminal' is the definition.
'pirate' can be an answer for 'criminal' (pirate is a kind of criminal). I am unsure of the 'main' bit.
'page that is about traitor' is the wordplay.
'page' becomes 'p'.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'about' means one lot of letters goes inside another.
'traitor' becomes 'rat' (rat can mean a treacherous person).
'ie' placed around 'rat' is 'irate'.
'p'+'irate'='PIRATE'
'and' is the link.
Can you help me to learn more?
(Other definitions for pirate that I've seen before include "Copy published material illegally" , "Illegal" , "Teach, perhaps" , "Penzance marauder ?" , "Robber on the high scas" .)