Old devil eats that and, after removing the wrappers, it's huge (9)
I believe the answer is:
leviathan
'huge' is the definition.
(thesaurus)
I can't explain the rest of the clue.
(Other definitions for leviathan that I've seen before include "Biblical sea monster" , "Monstrous beast" , "Biblical sea-monster" , "An evil hat turns to anything of great size" , "Huge (sea) monster" .)