Security is brought back into store (7)
I believe the answer is:
deposit
'security' is the definition.
(deposit is a kind of security)
'is brought back into store' is the wordplay.
'brought back' says the letters should be written backwards.
'into' is an insertion indicator.
'store' becomes 'depot' ('depot' can be a synonym of 'store').
'is' in reverse letter order is 'si'.
'si' placed inside 'depot' is 'DEPOSIT'.
(Other definitions for deposit that I've seen before include "Put into, bank account say" , "Plant" , "secure an item" , "Money given as security" , "Put down - initial payment" .)