Energetic, forceful (8)
I believe the answer is:
vigorous
This clue is a double definition.
'energetic' is the first definition.
(similar in meaning)
'forceful' is the second definition.
(synonyms)
(Other definitions for vigorous that I've seen before include "Strong and energetic" , "Full of energy and strength" , "energetic,strenuous" , "Strong, healthy" , "Energetic, forceful" .)