Get rid of king? No difficulty about that (5)
I believe the answer is:
erase
'get rid of' is the definition.
(I've seen this in another clue)
'king? no difficulty about that' is the wordplay.
'king?' becomes 'R' (abbreviation for rex, king in Latin).
'no difficulty' becomes 'ease' (ease is the opposite of difficulty).
'about that' means one lot of letters goes inside another.
'r' placed inside 'ease' is 'ERASE'.
(Other definitions for erase that I've seen before include "To remove all trace" , "Remove from memory" , "Remove evidence of" , "Rub out, expunge" , "Take out" .)