Savage punch, with force rather than power (6)
I believe the answer is:
fierce
'savage' is the definition.
(synonyms)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for fierce that I've seen before include "intensity" , "Violent in temper or manner" , "Wild and savage" , "Violent in manner or action" , "Barbarous" .)