Storehouse or department containing nothing (5)
I believe the answer is:
depot
'storehouse' is the definition.
(I know that storehouse can be written as depot)
'department containing nothing' is the wordplay.
'department' becomes 'dept'.
'containing' means one lot of letters goes inside another.
'nothing' becomes 'O' (looks like zero - 0).
'dept' going around 'o' is 'DEPOT'.
'or' is the link.
(Other definitions for depot that I've seen before include "Bus station in the US" , "Storage place" , "Supply base" , "Storehouse or warehouse" , "Headquarters - storehouse" .)