Military waking signal (8)
I believe the answer is:
reveille
'military waking signal' is the definition.
(I've seen this before)
This is the entire clue.
(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" .)