It's a crime to break the cease-fire (9)
I believe the answer is:
armistice
'cease-fire' is the definition.
(I know that truce can be written as armistice)
'it's a crime to break' is the wordplay.
'to break' is an anagram indicator.
'its'+'a'+'crime'='itsacrime'
'itsacrime' anagrammed gives 'ARMISTICE'.
'the' is the link.
(Other definitions for armistice that I've seen before include "Cease-fire in order to conduct talks" , "Truce" , "Suspension of hostilities" , "let-up from war" , "Fire is prevented by this" .)