Cast in outbuilding (4)
I believe the answer is:
shed
I believe this is a double definition.
'cast' is the first definition.
(I know that cast can be written as shed)
'outbuilding' is the second definition.
(I know that shed is a type of outbuilding)
'in' acts as a link.
(Other definitions for shed that I've seen before include "Small hut - lose it" , "Discard; small building" , "Small outbuilding" , "Lose as trees do leaves" , "tools found here?" .)