Some nibbled a mild cheese (4)
I believe the answer is:
edam
'cheese' is the definition.
(I know that Edam is a type of cheese)
'some nibbled a mild' is the wordplay.
'some' says the answer is hidden in the clue (some parts of the word are used).
'EDAM' can be found hidden inside 'nibbled a mild'.
(Other definitions for edam that I've seen before include "Hard Dutch cheese" , "Red-coated cheese" , "Sphere of Dutch cheese" , "Cheese made badly" , "edible sphere" .)