Behemoths (6)
I believe the answer is:
giants
'behemoths' is the definition.
('giant' can be a synonym of 'behemoth')
This is the entire clue.
(Other definitions for giants that I've seen before include "Behemoths, titans" , "they're big" , "men of great power?" , "eg The inhabitants of Brobdingnag" , "Behbmoths, titans" .)