I broadcast concert around end of September? Not right! (9)
I believe the answer is:
incorrect
'not right' is the definition.
('incorrect' is the opposite to 'right')
'i broadcast concert around end of september?' is the wordplay.
'broadcast' is an anagram indicator.
'around end of' indicates one should take the final letters.
The final letter of 'september' is 'r'.
'concert'+'r'='concertr'
'concertr' anagrammed gives 'ncorrect'.
'i'+'ncorrect'='INCORRECT'
(Other definitions for incorrect that I've seen before include "Not accurate" , "False, wrong" , "Place of refuge" , "Erroneous" .)