Something stale in the fridge? That's unlucky (4,6)
I believe the answer is:
hard cheese
I believe this is a double definition.
'something stale in the fridge?' is the first definition.
(hard or stale cheese)
'that's unlucky' is the second definition.
(phrase used to tell someone something is hard luck)
(Other definitions for hard cheese that I've seen before include "Leicester" , "Eighteen [EMMENTAL], for instance" , "Bad luck! (Grate it!)" , "Tough luck (informal)" , "Expression of sympathy" .)