Later on, I'm performing circus act (4-5)
I believe the answer is:
lion-tamer
'circus act' is the definition.
(I've seen this before)
'later on i'm performing' is the wordplay.
'performing' is an anagram indicator (the letters move around or 'perform').
'later'+'on'+'im'='lateronim'
'lateronim' with letters rearranged gives 'LION-TAMER'.
(Other definitions for lion-tamer that I've seen before include "Circus entertainer" , "Circus performer" .)