Military waking signal (8)
I believe the answer is:
reveille
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">military waking signal</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for reveille that I've seen before include "Bugle call to awaken soldiers" , "call to start" , "Early morning sound in the barracks" , "Soldiers' wakening call" , "The get-out-of-bed bugle call" .)