Part with newspaper contributor, a traitor (5,9)
I believe the answer is:
fifth columnist
'a traitor' is the definition.
(fifth columnist is a kind of traitor)
'part with newspaper contributor' is the wordplay.
I cannot quite see how this works, but
'newspaper' could be 'ft' (Financial Times newspaper) and 'ft' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for fifth columnist that I've seen before include "addition to quartet of writers?" , "seen here appropriately!" , "infiltrator!" , "Traitor" , "Enemy agent" .)