Military melody (4)
I believe the answer is:
taps
'military melody' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for taps that I've seen before include "Bugs; valves" , "Exploits" , "Knocks lightly on the faucets" , "Knocks gently" , "Military signal and faucets" .)