Jam, or a piece of cheese, perhaps (5)
I believe the answer is:
wedge
'jam' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for wedge that I've seen before include "Jam" , "Splitting device" , "Tapering block" , "Significant amount of money (informal)" , "V-sign" .)