A character in literature? (6)
I believe the answer is:
letter
I believe this clue is a double definition.
'a character' is the first definition.
(letter is a kind of character)
'literature?' is the second definition.
(thesaurus)
'in' acts as a link.
(Other definitions for letter that I've seen before include "Piece of correspondence" , "Epistle, missive" , "A written form of communication" , "reference?" , "Character; missive" .)