Heaviest fencing sword (4)
I believe the answer is:
epee
'heaviest fencing sword' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for epee that I've seen before include "Type of sword" , "Fencing weapon" , "Fencing sword, heavier than a foil" , "Duelling weapon" , "sports equipment" .)