Perfects (5)
I believe the answer is:
hones
'perfects' is the definition.
('hone' can be a synonym of 'perfect')
This is all the clue.
(Other definitions for hones that I've seen before include "Sharpens on strap, say razor" , "Perfects, sharpens" , "Sharpens as on whetstone" , "Sharpens, like knife on stone" , "gets sharp" .)