That woman follows traitor in preference (6)
I believe the answer is:
rather
'in preference' is the definition.
(I've seen this before)
'that woman follows traitor' is the wordplay.
'that woman' becomes 'her' ('her' refers to a woman).
'follows' says to put letters next to each other.
'traitor' becomes 'rat' (rat can mean a treacherous person).
'her' after 'rat' is 'RATHER'.
(Other definitions for rather that I've seen before include "Preferably, instead" , "More precisely; instead of" , "On the contrary; more precisely" , "More willingly, by preference" , "Quite; on the contrary" .)