Ring agents about acting (2,5)
I believe the answer is:
on stage
'acting' is the definition.
(I've seen this before)
'ring agents about' is the wordplay.
'ring' becomes 'o'.
'about' is an anagram indicator.
'agents' anagrammed gives 'nstage'.
'o'+'nstage'='ON-STAGE'
(Other definitions for on stage that I've seen before include "for an audience to watch?" , "playing a part?" , "Travelling in coach" , "Performing" , "Treading the boards" .)