Bra cut every bust (6)
I believe the answer is:
breach
'bust' is the definition.
(thesaurus)
'bra cut every' is the wordplay.
'cut' means to remove the last letter.
'every' becomes 'each' (synonyms).
'bra' with its last letter taken off is 'br'.
'br'+'each'='BREACH'
(Other definitions for breach that I've seen before include "transgression" , "'Gap, break or hole (6)'" , "Violation of a promise" , "Open up" , "Break (in a wall, etc)" .)