Military encirclement (5)
I believe the answer is:
siege
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">military encirclement</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for siege that I've seen before include "Operation to capture a fort, for example" , "Offence in which fortified place is surrounded" , "Blockade of a fortified place" , "Persistent attack" , "Military operation surrounding a town" .)