Hone (4)
'hone' is the definition.
(I know that hone is a more specific form of the action sharpen)
This is all the clue.
(Other definitions for sharpen that I've seen before include "instrument secured by former nurse" , "Get keen" , "Make pointed" , "Put a point on" , "Put a keen edge on" .)
'hone' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for whet that I've seen before include "Edge" , "appetizer" , "'Sharpen, appetite say (4)'" , "Hone" , "Sharpen by grinding" .)