A blow with the fist (5)
I believe the answer is:
punch
'a blow with the fist' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for punch that I've seen before include "Thump" , "Judy's puppet husband" , "Puppet character, drink and tool for making holes" , "Seaside puppet character" , "Sock" .)