Relative cut applied to rejected writer (6)
I believe the answer is:
nephew
'relative' is the definition.
(nephew is a kind of relative)
'cut applied to rejected writer' is the wordplay.
'cut' becomes 'hew' (I've seen this before).
'applied to' is a charade indicator (letters next to each other).
'rejected' says the letters should be written backwards.
'writer' becomes 'pen' (I've seen this before).
'pen' backwards is 'nep'.
'hew' put after 'nep' is 'NEPHEW'.
(Other definitions for nephew that I've seen before include "A sibling's child" , "Edward V to Richard III relation" , "A young male relation" , "Has a duty (to do something)" , "Family relative" .)