Tremble, getting feeling about traitor (7)
I believe the answer is:
vibrate
'tremble' is the definition.
(I've seen this before)
'feeling about traitor' is the wordplay.
'feeling' becomes 'vibe' (I've seen this in another clue).
'about' means one lot of letters goes inside another.
'traitor' becomes 'rat' (rat can mean a treacherous person).
'vibe' enclosing 'rat' is 'VIBRATE'.
'getting' acts as a link.
(Other definitions for vibrate that I've seen before include "Oscillate rapidly" , "Shake, quiver, or throb" , "swing" , "Move rapidly to and fro" , "tremble" .)