Size, immensity (8)
I believe the answer is:
enormity
I believe this clue is a double definition.
'size' is the first definition.
(I know that enormity is a type of enormousness)
'immensity' is the second definition.
(I've seen this in another clue)
(Other definitions for enormity that I've seen before include "Atrociousness" , "Vastness - great crime" , "Great wickedness or huge size" , "act of wickedness?" , "Extreme wickedness or vastness" .)