Timely cue (6)
I believe the answer is:
prompt
I believe this is a double definition.
'timely' is the first definition.
(synonyms)
'cue' is the second definition.
(synonyms)
(Other definitions for prompt that I've seen before include "Quick - cue" , "Cue; punctual" , "Cue given to actor" , "Whisper line to forgetful actor" , "Immediate - supply actor's lines" .)