Without penalty (4-4)
I believe the answer is:
scot-free
'without penalty' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for scot-free that I've seen before include "Entirely without penalty or injury" , "Without harm or loss" , "Secret of being unpunished - like Jock?" , "'Without any punishment whatsoever (4,4)'" , "Unscathed" .)