Offended by earls entertaining bishop and duke (5)
I believe the answer is:
erred
'offended' is the definition.
(err can mean to offend morally)
'earls entertaining bishop and duke' is the wordplay.
'earls' becomes 'ee' (an abbreviation for earl written twice).
'entertaining' indicates putting letters inside (inviting in, as for dinner).
'bishop' becomes 'rr' (abbreviation for Right Reverend).
'and' says to put letters next to each other.
'duke' becomes 'd' (abbreviation).
'ee' placed around 'rr' is 'erre'.
'erre'+'d'='ERRED'
'by' acts as a link.
(Other definitions for erred that I've seen before include "Made a mistake, was wrong" , "Made mistake, was incorrect" , "Sinned" , "Committed a sin" , "Strayed from the straight and narrow" .)