What secures heavy artillery initially north of city near Kyiv (7)
I believe the answer is:
hairpin
If this is the answer, I'm afraid I cannot explain it.
Can you help me to learn more?
(Other definitions for hairpin that I've seen before include "Sharp type of bend" , "associated with locks" , "Curving sharply" , "Device for fastening one's locks" , "stuck in a lock?" .)