Said to be a conflicted character's mask (4)
I believe the answer is:
hide
'mask' is the definition.
(both can mean to conceal or cover up)
'said to be a conflicted character's' is the wordplay.
'said to be' shows a homophone (sound like).
'a conflicted character' becomes 'Hyde' (as in Dr Jekyll and Mr Hyde).
'hyde' sounds like 'HIDE'.
(Other definitions for hide that I've seen before include "Conceal, veil" , "Secrete, conceal" , "Tanned skin of an animal" , "Once told, hurried < to > conceal" , "Animal retreat" .)