He is all the more ready to help forgetful actors (8)
I believe the answer is:
prompter
'he is all the more' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'ready to help forgetful actors' is the wordplay.
I cannot really understand how this works, but
'ready' could be 'prompt' (similar in meaning) and 'prompt' is found in the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for prompter that I've seen before include "One helping actors with lines" , "One helping actors - much quicker" , "I suggest" , "Theatre worker" , "Supplier of lines in the theatre" .)