Relatives installing large oven (4)
I believe the answer is:
kiln
'oven' is the definition.
(I know that kiln is a type of oven)
'relatives installing large' is the wordplay.
'relatives' becomes 'kin' (I've seen this in another clue).
'installing' indicates putting letters inside (I've seen this in other clues).
'large' becomes 'L' (eg in clothes sizes).
'kin' placed around 'l' is 'KILN'.
(Other definitions for kiln that I've seen before include "Oven for firing bricks" , "Oven for firing pottery" , "Oven for firing ceramics etc" , "Large commercial oven" , "Large oven, for potters say" .)