Sharpening or perfecting (6)
I believe the answer is:
honing
This clue is a double definition.
'sharpening' is the first definition.
(honing is a kind of sharpening)
'perfecting' is the second definition.
('hone' can be a synonym of 'perfect')
(Other definitions for honing that I've seen before include "Sharpening on a stone" , "Making sharp" , "Sharpening, say razor" .)