Brought up nonsense about performer (5)
I believe the answer is:
actor
'performer' is the definition.
(actor is a kind of performer)
'brought up nonsense about' is the wordplay.
'brought up' is a reversal indicator (down clues only).
'nonsense' becomes 'rot' (I've seen this before).
'about' becomes 'ca' (abbreviation for 'circa'**).
'rot'+'ca'='rotca'
'rotca' back-to-front is 'ACTOR'.
(Other definitions for actor that I've seen before include "Theatrical performer" , "One taking part" , "For example, Colman" , "Croat (anag.)" , "One in a play" .)