Cut pork luncheon meat slightly more than halfway through loaf into 8 sections.
Place pork in 1-quart casserole.
Spread 1/2 teaspoon mustard between every other cut.
Insert 1/2 slice apple ring in each cut; top with remaining 1/2 slice apple ring.
Insert whole cloves in apple rings if desired.
Sprinkle brown sugar over pork.
Cover tightly and microwave on high (100%) until pork is hot, 5 to 7 minutes.
Let stand 3 minutes.