Hide son with relatives (4)
I believe the answer is:
skin
'hide' is the definition.
(a hide is an animal skin)
'son with relatives' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'with' is a charade indicator (letters next to each other).
'relatives' becomes 'kin' (kin can mean relatives or family).
's'+'kin'='SKIN'
(Other definitions for skin that I've seen before include "Outer layer of, eg, apple" , "What keeps you in" , "Thin outer layer" , "External surface" , "Outer surface" .)