1: Boxer Max returned, holding heroin, for treatment (5)
2: Period email feature (3)
3: A date in February: good time for a massacre? (10,3)
5: Deranged parent has right to become a spouse (7)
6: One later enters, like, with matching sides (11)
7: Went ahead and used the power button (7,2)
10: Ships use up aid at sea; remain in a grave situation (4,2,7)
12: Wizards covered in liquor and beer...it might be for charity (7, 4)
13: The end, you say? On the contrary! (3)
15: Vaudeville star to lead opening of Angela's Grandma (3,6)
18: Certain styles of class sat uneasily (7)
19: Frost to cover the cake (3)
24: Retro eatery has nothing covered in grease (5)
26: Sheep to start wallowing in ease (3)
28: Bounder beheaded by slippery swimmer (3)