One of five to follow Charles, essentially a buffoon! (9)
I believe the answer is:
harlequin
'a buffoon' is the definition.
(I know that harlequin is a type of buffoon)
'one of five to follow charles essentially' is the wordplay.
'one of five' becomes 'quin' (short for quintuplet, one of five children).
'to follow' means one lot of letters go next to another (some letters go after or follow others).
'essentially' says to take the centre.
The central letters of 'charles' are 'harle'.
'quin' put after 'harle' is 'HARLEQUIN'.
(Other definitions for harlequin that I've seen before include "Traditional pantomime character" , "Brightly-coloured - Columbine's partner in pantomime" , "Character in a diamond-patterned costume - variegated" , "London rugby player" , "Pantomime character in a tight spangled costume" .)