Maybe egoists changing gradually (2,4,4,2)
I believe the answer is:
as time goes by
'gradually' is the definition.
'maybe egoists changing' is the wordplay.
'changing' is an anagram indicator.
'maybe'+'egoists'='maybeegoists'
'maybeegoists' is an anagram of 'AS TIME GOES BY'.
(Other definitions for as time goes by that I've seen before include "Play it, Sam. Play - (Casablanca)" , "Song you must remember" , "through the years?" .)