Crude oil's in store (4)
I believe the answer is:
silo
'store' is the definition.
(a store of crops)
'crude oil's' is the wordplay.
'crude' is an anagram indicator.
'oils' with letters rearranged gives 'SILO'.
'in' is the link.
(Other definitions for silo that I've seen before include "Grain storage tower" , "Farm store; soil (anag.)" , "Grain storage area" , "Storage space for fodder" , "Missile pit" .)