Family has large oven (4)
I believe the answer is:
kiln
'oven' is the definition.
(I know that kiln is a type of oven)
'family has large' is the wordplay.
'family' becomes 'kin' (synonyms).
'has' is an insertion indicator.
'large' becomes 'L' (eg in clothes sizes).
'kin' enclosing 'l' is 'KILN'.
(Other definitions for kiln that I've seen before include "Oven for firing pottery" , "Oven for hardening and drying" , "Pottery-firing oven" , "Potter's Friend" , "Furnace, oven" .)