One who urges on players from the wings (8)
I believe the answer is:
prompter
This could be a double definition.
'one who urges' is the first definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'players from the wings' is the second definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe there's a link between them I don't understand?
'on' is the link.
Can you help me to learn more?
(Other definitions for prompter that I've seen before include "One helping actors with lines" , "to be ready earlier" , "Drying actor's helper" , "Theatre worker" , "to give help on the line?" .)