Military wake-up call (8)
I believe the answer is:
reveille
'military wake-up call' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for reveille that I've seen before include "The wake-up army bugle call" , "Signal to awaken soldiers at daybreak" , "Summons to get up" , "Bugle call to awaken soldiers" , "Army bugle call to get out of bed" .)