Minor offence or transgression (12)
I believe the answer is:
misdemeanour
This clue is a double definition.
'minor offence' is the first definition.
(I've seen this before)
'transgression' is the second definition.
(I know that misdemeanour is a type of offence)
(Other definitions for misdemeanour that I've seen before include "Minor wrongdoing" , "Minor violation" , "Minor offence" .)