Shot protecting leader in military post (4)
I believe the answer is:
jamb
'post' is the definition.
(I've seen this before)
'shot protecting leader in military' is the wordplay.
'shot' becomes 'jab' (I can't explain this - if you can you should give a lot more credence to this answer).
'protecting' is an insertion indicator.
'leader in' says to take the initial letters.
The initial letter of 'military' is 'm'.
'jab' enclosing 'm' is 'JAMB'.
Can you help me to learn more?
(Other definitions for jamb that I've seen before include "Side of door frame" , "Side post of a doorway" , "bit on the side?" , "Part of door frame" , "part of doorway?" .)