On time (8)
'on time' is the definition.
(synonyms)
This is all the clue.
(Other definitions for prompt that I've seen before include "Whisper line to forgetful actor" , "Refresh the memory -- on time" , "Bring about; actors' help" , "Supply a forgotten line to an actor" , "Help struggling actor" .)
'on time' is the definition.
(similar in meaning)
This is all the clue.
(Other definitions for punctual that I've seen before include "Happening at the agreed time" , "Exactly on time" , "Arriving on time" , "Always on time for appointments" , "Bang on time" .)