Forceful, energetic (7)
I believe the answer is:
dynamic
I believe this clue is a double definition.
'forceful' is the first definition.
(similar in meaning)
'energetic' is the second definition.
(associated in meaning)
(Other definitions for dynamic that I've seen before include "Vigorous and effective" , "Having power" , "Driving" , "Very active" , "Powerful and vigorous" .)