What detains Dickens hero before every realisation (8)
I believe the answer is:
epiphany
'realisation' is the definition.
(an epiphany is a revelation)
'what detains dickens hero before every' is the wordplay.
'what' becomes 'eh' (sound used to ask 'what?' or 'pardon?').
'detains' is an insertion indicator.
'dickens hero' becomes 'Pip' (main character in Great Expectations).
'before' is a charade indicator (letters next to each other).
'every' becomes 'any' (every member can be any of them).
'eh' enclosing 'pip' is 'epiph'.
'epiph'+'any'='EPIPHANY'
(Other definitions for epiphany that I've seen before include "Sudden realisation" , "Its events occur in Matthew" , "revelation results" , "Christian feast of showing Christ to Magi" , "Christian festival of Magi visiting Chirst, celebrated on 6th January" .)