Beyond big (4)
(Other definitions for epic that I've seen before include "Long, heroic story" , "Long poem telling of heroic events" , "imposing" , "eg Beowulf" , "Long poem set in nice picture" .)
'beyond big' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for huge that I've seen before include "Vast; immense" , "Mammoth" , "Massive" , "Jumbo" , "giant" .)
(Other definitions for gigantic that I've seen before include "Huge, enormous" , "Fantastically great" , "Titanic" , "Thumping" , "Stupendous" .)