Largest fencing sword (4)
I believe the answer is:
epee
'largest 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 "Fencing sword similar to a foil" , "Type of sword" , "Fighting blade" , "Duelling weapon" , "sharp-edged implement" .)