If you say
that someone has been let loose
in a place or situation, you mean that they have been given complete freedom
to do what they like in that place or situation, and you suggest
that this may be risky
She has all the glee of a little girl let loose in a sweetie shop.
Trainees go through a four-hour lesson before they are let loose on the controls.
COBUILD Advanced English Dictionary. Copyright © HarperCollins Publishers