Blade worn needs edges switched (6)
I believe the answer is:
dagger
'blade' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for dagger that I've seen before include "Murder weapon" , "Stabbing weapon" , "Hand weapon" , "Short knife for stabbing" , "''Is this a ... which I see before me'' (Macbeth)" .)