Corn one stored in puzzling place (5)
I believe the answer is:
maize
'corn' is the definition.
(I know that corn can be written as Maize)
'one stored in puzzling place' is the wordplay.
'one' becomes 'i' (Roman numeral).
'stored in' indicates putting letters inside.
'puzzling place' becomes 'maze' (a maze is like a puzzle).
'i' placed inside 'maze' is 'MAIZE'.
(Other definitions for maize that I've seen before include "one could make a meal of it" , "Corncob plant" , "Cereal crop" , "Tall cereal grass producing large edible ears" , "Indian corn" .)