Sharpness wins fight -- heads are knocked off (7)
I believe the answer is:
insight
'sharpness' is the definition.
(thesaurus)
'wins fight heads are knocked off' is the wordplay.
'wins' becomes 'ins' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'heads are knocked off' means to remove the first letter.
'fight' with its initial letter taken away is 'ight'.
'ins'+'ight'='INSIGHT'
Can you help me to learn more?
(Other definitions for insight that I've seen before include "what psychoanalysts hope to gain" , "Deep understanding" , "Sudden understanding" , "Clear understanding" , "Awareness" .)