in safety—
1. in a safe state or position:
- Cut off by the rising waters, the boys climbed on to a ledge of rock, where they remained in safety.
2. do smth. without running any risk:
- The people of this city can go where they want to go, do what they have to do and do it in safety.
with safety — = in safety 2:
- That ladder looks rather rickety; don’t attempt to climb it unless you are sure you can do it with safety.