Thin rakes in back of storeroom? Correct (6)
I believe the answer is:
remedy
'correct' is the definition.
(remedying is a kind of correcting)
'thin rakes in' is the wordplay.
'thin' becomes 'reedy' (as in a thin or reedy voice).
'rakes' becomes 'm' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in' indicates putting letters inside.
'reedy' going around 'm' is 'REMEDY'.
'back of storeroom?' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for remedy that I've seen before include "Countermeasure" , "Medicine or therapy that cures disease or relieves pain" , "answer" , "Medicine, treatment" , "Nostrum" .)