Something huge or monstrous (8)
I believe the answer is:
behemoth
'something huge or monstrous' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for behemoth that I've seen before include "Monstrous beast, or thing" , "Great beast of the Bible" , "Big corporation" , "Huge organisation" , "Anything abnormally large and powerful" .)