All one's possessions stored in highest ateliers (6)
I believe the answer is:
estate
'all one's possessions' is the definition.
'stored in highest ateliers' is the wordplay.
'stored in' indicates the answer is hidden within the clue.
'ESTATE' is hidden in the letters of 'highest ateliers'.
(Other definitions for estate that I've seen before include "Tea-set (anag.)" , "Property - tea set (anag)" , "Area of landed property" , "Land with buildings" , "Country property" .)