Pardon me - nasty new arrangement (7)
I believe the answer is:
amnesty
'pardon' is the definition.
(I know that pardon can be written as amnesty)
'me nasty new arrangement' is the wordplay.
'new arrangement' is an anagram indicator (I've seen this in other clues).
'me'+'nasty'='menasty'
'menasty' anagrammed gives 'AMNESTY'.
(Other definitions for amnesty that I've seen before include "International organisation concerned with human rights" , "General pardon, usually political" , "suspension of law" , "A general political pardon, perhaps for tax defaulters" , "A general pardon for nasty me" .)