Powerful, vehement (7)
I believe the answer is:
intense
I believe this is a double definition.
'powerful' is the first definition.
(intense can mean powerful or profound)
'vehement' is the second definition.
(similar in meaning)
(Other definitions for intense that I've seen before include "Teen sin (anag.)" , "Strongly felt" , "Strong in quality or degree - perhaps a feeling" , "Of extreme force" , "In an extreme degree" .)