Cupboard key? (6)

I believe the answer is:

locker

I believe this is a double definition.

'cupboard' is the first definition.
(I've seen this before)

'key?' is the second definition.
(I've seen this before)

(Other definitions for locker that I've seen before include "Small compartment where things can be securely stored" , "key" , "Storage unit for personal possessions" , "Small cupboard for personal use" , "Small securable cupboard" .)

I've seen this clue in The Sun and The Telegraph.

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