Prompt brief mention in performance (2,4)
I believe the answer is:
on time
'prompt' is the definition.
(synonyms)
'brief mention in performance' is the wordplay.
I cannot quite see how this works, but
'in performance' could be 'on' and 'on' is found within the answer.
The remaining letters 'time' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for on time that I've seen before include "as expected" , "according to schedule" , "Not running late" , "Prompt" , "Punctual, not late" .)