Small family film (4)
I believe the answer is:
skin
'film' is the definition.
(I've seen this in other clues)
'small family' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'family' becomes 'kin' (synonyms).
's'+'kin'='SKIN'
(Other definitions for skin that I've seen before include "Peel; drum head" , "coat" , "Epidermis - peel" , "What keeps you in" , "Outer layer of, eg, apple" .)