Behemoths, titans (6)
I believe the answer is:
giants
I believe this clue is a double definition.
'behemoths' is the first definition.
('giant' can be a synonym of 'behemoth')
'titans' is the second definition.
('giant' can be a synonym of 'titan')
(Other definitions for giants that I've seen before include "Large mythical beings" , "they're big" , "Huge legendary beings" , "men of great power?" , "eg The inhabitants of Brobdingnag" .)