A storage tower erected contains produce for citadel (9)
I believe the answer is:
acropolis
'for citadel' is the definition.
(acropolis is a kind of citadel)
'a storage tower erected contains produce' is the wordplay.
'storage tower' becomes 'silo' (tower for storing grain on a farm).
'erected' shows that the letters should be reversed in order (in a down clue, letters go up).
'contains' is an insertion indicator.
'produce' becomes 'crop' (I've seen this before).
'silo' in reverse letter order is 'olis'.
'a'+'olis'='aolis'
'aolis' placed around 'crop' is 'ACROPOLIS'.
(Other definitions for acropolis that I've seen before include "Imposing building" , "Ancient citadel of Athens" , "Upper fortified part of Greek city as in Athens" , "Parthenon location" , "Greek tourist spot" .)