Sword, the sharp blade broke finally (4)
I believe the answer is:
epee
'sword' is the definition.
(sword used in fencing)
'the sharp blade broke finally' is the wordplay.
'finally' indicates one should take the final letters.
The last letters of 'the sharp blade broke' are 'EPEE'.
(Other definitions for epee that I've seen before include "Narrow fencing sword" , "Bit of fencing" , "Sharp-pointed duelling sword" , "there's a point to it" , "Fencer's sword" .)