With string? Break into breach? (9)
I believe the answer is:
violation
'breach?' is the definition.
(I've seen this before)
'with string? break into' is the wordplay.
'with' is an insertion indicator.
'string?' becomes 'viola' (viola is a kind of string).
'break' is an anagram indicator.
'into' anagrammed gives 'tion'.
'viola' put into 'tion' is 'VIOLATION'.
(Other definitions for violation that I've seen before include "outrage" , "abuse" , "Offence" , "Breach" , "Infringement" .)