Narcissist (6)
I believe the answer is:
egoist
'narcissist' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for egoist that I've seen before include "It goes around with conceited fellow" , "Self-centred person with a swelled head" , "Narcissist" , "Self-absorbed person" , "A self-interested conceited person" .)