Store Greek character wants up North (4)
I believe the answer is:
silo
'store greek' is the definition.
'silo' can be an answer for 'store' (a store of crops). I'm unsure of the 'greek' bit.
'character wants up north' is the wordplay.
'character' becomes 'o'.
'wants up' becomes 'lis' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'north' is a reversal indicator (in a down clue, letters go up or 'north').
'o'+'lis'='olis'
'olis' written backwards gives 'SILO'.
Can you help me to learn more?
(Other definitions for silo that I've seen before include "Grain storage area" , "Storage space for fodder" , "Store for grain or fodder" , "Tower for storing grain" , "Missile launcher; farm store" .)