It's a crime breaking ceasefire (9)
I believe the answer is:
armistice
'ceasefire' is the definition.
(I've seen this before)
'it's a crime breaking' is the wordplay.
'breaking' indicates anagramming the letters.
'its'+'a'+'crime'='itsacrime'
'itsacrime' anagrammed gives 'ARMISTICE'.
(Other definitions for armistice that I've seen before include "End of hostilities" , "Agreement during war to suspend fighting" , "Cease-fire in order to conduct talks" , "let-up from war" , "Fire is prevented by this" .)