Notable intimation to those on the track (6)
I believe the answer is:
signal
'notable' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for signal that I've seen before include "Not noise" , "Sign that conveys a message" , "(Traffic) light" , "Indication; a train control" , "Remarkable; gesture" .)