Warning, old-style (6)
I believe the answer is:
alarum
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">warning old-style</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 alarum that I've seen before include "Warning sound" , "disturbance" , "conflict" , "Warning bell (archaic)" , "commotion" .)