Hide family beneath roof of synagogue (4)
I believe the answer is:
skin
'hide' is the definition.
(a hide is an animal skin)
'family beneath roof of synagogue' is the wordplay.
'family' becomes 'kin' (synonyms).
'beneath' says to put letters next to each other (in a down clue, some letters go below others).
'roof of' suggests taking the first letters (in a down clue, the top letter).
The initial letter of 'synagogue' is 's'.
'kin' put after 's' is 'SKIN'.
(Other definitions for skin that I've seen before include "Outer covering" , "External membrane of body" , "Peel; drum head" , "Living tissue" , "Fell" .)