Performing 'Carmen', tenor's showing grievance (12)
I believe the answer is:
remonstrance
'grievance' is the definition.
(thesaurus)
'performing carmen tenor's' is the wordplay.
'performing' is an anagram indicator.
'carmen'+'tenors'='carmentenors'
'carmentenors' is an anagram of 'REMONSTRANCE'.
'showing' is the link.
(Other definitions for remonstrance that I've seen before include "complaint" , "Strong protest" , "petition" .)