What attics are used for (7)
I believe the answer is:
storage
'what attics are used for' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for storage that I've seen before include "reservation?" , "Charge for use of warehouse" , "Depository space for goods" , "Stowage" , "Space available for keeping goods" .)