Touches on the shoulder (4)
I believe the answer is:
taps
'touches on the shoulder' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for taps that I've seen before include "Military bugle call at dusk" , "Thread cutters' strikes" , "Military signal to turn the lights out" , "The sound of lights out" , "Bugs; valves" .)