Blade's ego? (4)
I believe the answer is:
epee
This could be a double definition.
'blade's' is the first definition.
(epee is a kind of blade)
'ego?' is the second definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
(Other definitions for epee that I've seen before include "Fencing sword, heavier than a foil" , "Bit of fencing" , "Fencing weapon" , "Fencer's weapon" , "Narrow fencing sword" .)