Fed a mouse some cheese (4)
I believe the answer is:
edam
'cheese' is the definition.
(I know that Edam is a type of cheese)
'fed a mouse some' is the wordplay.
'some' indicates the answer is hidden within the clue.
'EDAM' is hidden within 'fed a mouse'.
(Other definitions for edam that I've seen before include "Hard Dutch cheese" , "Cheese made in Holland" , "Netherlands cheese" , "Sphere of Dutch cheese" , "something from the deli" .)