Biscuit containers the wrong way up (4)
I believe the answer is:
snap
'biscuit' is the definition.
(I've seen this before)
'containers the wrong way up' is the wordplay.
'containers' becomes 'pans' (pan is a kind of container).
'the wrong way up' says the letters should be written backwards (in a down clue, letters go up).
'pans' backwards is 'SNAP'.
(Other definitions for snap that I've seen before include "Break sharply - a simple card game" , "Break sharply like dried twig" , "Go to pieces < , it's said, quickly" , "Bite at or utter angry words" , "Speak sharply or break suddenly" .)