What egotist refers to repeatedly in behavioural trait (4)
I believe the answer is:
meme
'behavioural trait' is the definition.
(I've seen this before)
'what egotist refers to repeatedly' is the wordplay.
'what egotist refers to' becomes 'me'.
'repeatedly' shows that letters should be duplicated.
'me' duplicated is 'MEME'.
'in' is the link.
(Other definitions for meme that I've seen before include "Question that spreads on the internet" , "Cultural belief that assumes a life of its own" , "Concept that spreads rapidly on the Internet" , "Transmitted cultural idea" , "Image etc. that spreads rapidly on the Internet" .)