Get 'safe' or to be a 'safe character'
'fix up, look sharp, cmon, get dark'
Term used especially in the Midlands for a situation turning nasty. This can be a person and/or situation that was carefree and as lovely as a litter of cute kitties or puppies but is now like a litter of snarling pit bulls or other snarling like animals/creatures
"You can either leave (the situation) nicely or I am going to get DARK on you"