Both Telegraph and Herald are noteworthy (6)
I believe the answer is:
signal
'are noteworthy' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for signal that I've seen before include "Silent communication" , "Gesture to communicate" , "Gesture of communication" , "Electrical transmission; striking in importance" , "Communication by sign" .)