"Awesome, dude!" (4)
(Other definitions for rad that I've seen before include "measure of dangerous activity" , "Unit of radiation" .)
'awesome dude' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for epic that I've seen before include "Heroic, huge" , "Large-scale" , "Impressive scope" , "A long poem or book with adventurous theme" , "Long narrative poem telling of a hero's deeds" .)