Actor's hint (3)
I believe the answer is:
cue
'actor's hint' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cue that I've seen before include "Actor's line to remind another" , "Prompt; signal" , "Rod used in billiards" , "Signal to begin - tapered stick" , "Billiards stick" .)