Excuse, exempt from (3,3)
I believe the answer is:
let off
This clue is a double definition.
'excuse' is the first definition.
(I know that excuse can be written as let off)
'exempt from' is the second definition.
(thesaurus)
(Other definitions for let off that I've seen before include "Excuse or release of" , "Spare" , "Go easy on" , "Discharge (a firework)" , "Allow to escape punishment" .)