Lower oneself: dine out entertaining leader of gangsters (5)
I believe the answer is:
deign
'lower oneself' is the definition.
(thesaurus)
'dine out entertaining leader of gangsters' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'entertaining' means one lot of letters goes inside another.
'leader of' says to take the initial letters.
The initial letter of 'gangsters' is 'g'.
'dine' is an anagram of 'dein'.
'dein' enclosing 'g' is 'DEIGN'.
(Other definitions for deign that I've seen before include "Think fit" , "Think appropriate" , "Lower oneself" , "Do something considered to be below one's dignity" , "Seem supercilious" .)