On time to help forgetful actor (6)
I believe the answer is:
prompt
This clue is a double definition.
'on time' is the first definition.
(synonyms)
'help forgetful actor' is the second definition.
(I've seen this before)
'to' is the link.
(Other definitions for prompt that I've seen before include "Spurs do this" , "Speedy - help for forgetful actor" , "Reminder" , "Cue given to a performer" , "Immediate - supply actor's lines" .)