Hide small close relations (4)
I believe the answer is:
skin
'hide' is the definition.
(a hide is an animal skin)
'small close relations' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'close relations' becomes 'kin' (your kin are your family).
's'+'kin'='SKIN'
(Other definitions for skin that I've seen before include "Hide - flay" , "Outer covering" , "Living tissue" , "External surface" , "Protective body covering" .)