Mould in shed (4)
I believe the answer is:
cast
I believe this is a double definition.
'mould' is the first definition.
('cast' can be a synonym of 'mould')
'shed' is the second definition.
(thesaurus)
'in' is the link.
(Other definitions for cast that I've seen before include "Allot roles in a play" , "Troupe" , "Collectively, the actors in a play" , "Discard; mould" , "Get rid of" .)