Sharp? Sadly I’m no Caruso, I admitted! (11)
I believe the answer is:
acrimonious
'sharp?' is the definition.
(thesaurus)
'sadly i'm no caruso i admitted' is the wordplay.
'sadly' indicates anagramming the letters.
'admitted' is an insertion indicator.
'im'+'no'+'caruso'='imnocaruso'
'imnocaruso' anagrammed gives 'acrmonious'.
'acrmonious' placed around 'i' is 'ACRIMONIOUS'.
(Other definitions for acrimonious that I've seen before include "Hostile" , "Angry, bitter" , "Producing bad feelings" .)