Bolt or lock the cell door to prevent it (6)
I believe the answer is:
escape
'bolt' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for escape that I've seen before include "Get away from depravity" , "Elude; leakage" , "'Break free, get away (6)'" , "An outburst" , "Gain freedom" .)