Self-centered one (6)
I believe the answer is:
egoist
'self-centered one' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for egoist that I've seen before include "Conceited person with little regard for others" , "number one fan" , "It goes with self-centred man" , "Selfish type" , "Person with very a good opinion of himself" .)