Hide small family members (4)
I believe the answer is:
skin
'hide' is the definition.
(a hide is an animal skin)
'small family members' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'family members' becomes 'kin' (kin means one's relations).
's'+'kin'='SKIN'
(Other definitions for skin that I've seen before include "Remove the outer layer" , "Outer layer of tissue" , "Hide - flay" , "Flense" , "Outer layer of a fruit or vegetable" .)