Lower oneself to be entertained by rude ignoramus (5)
I believe the answer is:
deign
'lower oneself' is the definition.
(thesaurus)
'entertained by rude ignoramus' is the wordplay.
'entertained by' indicates the answer is hidden within the clue.
'DEIGN' is hidden in the letters of 'rude ignoramus'.
'to be' acts as a link.
(Other definitions for deign that I've seen before include "See fit" , "consent" , "Do something considered to be below one's dignity" , "Be pleased" , "Think fit" .)