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' indicates anagramming the letters.
'oils' is an anagram of 'SILO'.
'in' acts as a 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" .)