Onset of crime overlooked in grounds (6)
I believe the answer is:
reason
'grounds' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for reason that I've seen before include "Cause; mind's power" , "Ability to think rationally" , "brain operations" , "Justification needed" , "Motivation or justification" .)