Drum signal (6)
I believe the answer is:
tattoo
'drum signal' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tattoo that I've seen before include "that takes some beating?" , "Military display - skin design" , "drawing on arms, perhaps" , "Military entertainment or skin adornment" , "Indelible impression" .)