Cue (6)
'cue' is the definition.
(prompt is a kind of cue)
This is the entire clue.
(Other definitions for prompt that I've seen before include "Reminder" , "Immediate - remind of lines" , "Supply a forgotten line to an actor" , "Arriving on time" , "Cause; on time" .)
'cue' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for signal that I've seen before include "Not noise" , "Message in the form of a gesture" , "beacon" , "Gesture with meaning" , "Non-verbal action with an encoded message" .)