Performer rejected new routine (4)
I believe the answer is:
turn
'performer' is the definition.
('turn' can mean a performer as well as their act)
'rejected new routine' is the wordplay.
'rejected' is a reversal indicator.
'new' becomes 'n'.
'routine' becomes 'rut' (rut is a kind of routine).
'n'+'rut'='nrut'
'nrut' written backwards gives 'TURN'.
(Other definitions for turn that I've seen before include "Revolve - go off" , "Move around an axis, or change" , "Rotate - go" , "Move in a new direction" , "Sour" .)