A remarkable cue (6)
I believe the answer is:
signal
This clue is a double definition.
'a remarkable' is the first definition.
(signal can mean striking or noteworthy)
'cue' is the second definition.
(I've seen this before)
(Other definitions for signal that I've seen before include "Alert" , "Gesture to communicate" , "Not noise" , "Gesture giving information or command" , "intimation" .)