Old saw having lost its edge? (6)
I believe the answer is:
cliche
'old saw' is the definition.
(I've seen this in another clue)
I don't understand the rest of the clue.
(Other definitions for cliche that I've seen before include "Chestnut" , "Phrase made tedious through repetition" , "Hackneyed phrase or idea" , "Over-used saying, hackneyed phrase" , "Tag" .)