Traitor – informant (3)
I believe the answer is:
rat
I believe this clue is a double definition.
'traitor' is the first definition.
(rat can mean a treacherous person)
'informant' is the second definition.
(rat is a kind of informant)
(Other definitions for rat that I've seen before include "Unpleasant character" , "Sewer rodent" , "Unpopular rodent" , "one escaping doomed vessel?" , "Despicable person" .)