Hide small relatives (4)
I believe the answer is:
skin
'hide' is the definition.
(a hide is an animal skin)
'small relatives' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'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 tissue" , "Surface layer" , "Outer layer of, eg, apple" , "Living tissue" , "Swindle" .)