Hide capital for Swiss family (4)
I believe the answer is:
skin
'hide' is the definition.
(a hide is an animal skin)
'capital for swiss family' is the wordplay.
'capital for' suggests taking the first letters.
'family' becomes 'kin' (synonyms).
The initial letter of 'swiss' is 's'.
's'+'kin'='SKIN'
(Other definitions for skin that I've seen before include "Peel; drum head" , "What keeps you in" , "External surface" , "Living tissue" , "Outer layer of, eg, apple" .)