Hide from ultimately hideous family (4)
I believe the answer is:
skin
'hide' is the definition.
(a hide is an animal skin)
'ultimately hideous family' is the wordplay.
'ultimately' suggests the final letters.
'family' becomes 'kin' (synonyms).
The final letter of 'hideous' is 's'.
's'+'kin'='SKIN'
'from' acts as a link.
(Other definitions for skin that I've seen before include "Pelt" , "Surface layer" , "Outer surface" , "Dermis" , "External membrane of body" .)