Family member with a really empty store (7)
I believe the answer is:
granary
'store' is the definition.
(I know that granary is a type of store)
'family member with a really empty' is the wordplay.
'family member' becomes 'gran' (short for grandmother).
'with' says to put letters next to each other.
'empty' means to remove the middle letters.
'really' with its middle removed is 'ry'.
'gran'+'a'+'ry'='GRANARY'
(Other definitions for granary that I've seen before include "Harvest store" , "Store for, eg, corn" , "Store for grain, etc" , "breadbasket" , "Grain storehouse" .)