Enormousness (9)
I believe the answer is:
greatness
'enormousness' is the definition.
(I know that enormousness can be written as greatness)
This is the entire clue.
(Other definitions for greatness that I've seen before include "Malvolio wasn't to fear being thrust into?" , "Magnitude; eminence" , "Nobility" , "Natal attribute or achievement or something thrust upon one!" , "Fame and importance" .)