Prompts copper on points (4)
I believe the answer is:
cues
'prompts' is the definition.
('cue' can be a synonym of 'prompt')
'copper on points' is the wordplay.
'copper' becomes 'cu' (chemical symbol).
'on' means one lot of letters go next to another.
'points' becomes 'es' (E is an example**).
'cu'+'es'='CUES'
(Other definitions for cues that I've seen before include "Signals for action" , "Snooker rods" , "Snooker ball strikers" , "Prompts for action" , "Actor's signal" .)