Box without risk (4)
I believe the answer is:
'box' is the definition.
(safe is a kind of box)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for safe that I've seen before include "Secure - place in the bank", "Iron box in which to keep money or important papers", "Free from risk", "Secure cupboard", "Strong metal box to store valuables".)