Tons about time for performing (7)
I believe the answer is:
onstage
'for performing' is the definition.
(I've seen this before)
'tons about time' is the wordplay.
'about' indicates an anagram.
'time' becomes 'age' (an age is a period of time).
'tons' anagrammed gives 'onst'.
'onst'+'age'='ONSTAGE'
(Other definitions for onstage that I've seen before include "Visible to theatregoers" , "(Of actor) visible to the audience" , "Facing house" , "performing in the theatre?" , "In view of house" .)