Gardening tool to sharpen, not new (3)
I believe the answer is:
hoe
'gardening tool' is the definition.
(I've seen this before)
'sharpen not new' is the wordplay.
'sharpen' becomes 'hone' (honing is a kind of sharpening).
'not' is a deletion indicator.
'new' becomes 'n'.
'hone' with 'n' taken out is 'HOE'.
'to' acts as a link.
(Other definitions for hoe that I've seen before include "Plymouth - -" , "Garden tool for scraping up weeds" , "Weeder" , "Weeding tool" , "Use garden tool" .)