Not subject to taxes (6)
I believe the answer is:
exempt
'not subject to taxes' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for exempt that I've seen before include "Free (from taxes, etc)" , "Absolved" , "Not liable, as others may be" , "Immune - absolve" , "Not subject to a law" .)