Post-WWII alliance
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">post-wwii alliance</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for nato that I've seen before include "Atlantic alliance (abbr.)" , "Military organization" , "N. Atlantic alliance" , "Security agreement" , "Western mil. alliance" .)