Made up cheese (4)
I believe the answer is:
edam
'cheese' is the definition.
(I know that Edam is a type of cheese)
'made up' is the wordplay.
'up' says the letters should be written backwards (in down clue: letters go upwards).
'made' in reverse letter order is 'EDAM'.
(Other definitions for edam that I've seen before include "something from the deli" , "Mild yellow Dutch cheese" , "Cheese made in Holland" , "Hard Dutch cheese" , "Made into a nice cheese" .)