Crossword Genius

Put an edge on ballpoint after rash redraft (7)

Ross

I believe the answer is:

sharpen

I'm a little stuck... Click here to teach me more about this clue!

'put an edge on' is the definition.
I can't judge whether this definition defines the answer.

'ballpoint after rash redraft' is the wordplay.
I cannot really see how this works, but
'ballpoint' could be 'pen' (I've seen this in another clue) and 'pen' is found within the answer.
an anagram of 'rash' is 'shar' which is located in the answer.
No letters remain.
This may be the basis of clue (or it may be nonsense).

Can you help me to learn more?

(Other definitions for sharpen that I've seen before include "Put a keen edge on" , "Hone (a knife blade)" , "Make pointed" , "Get keen" , "Put a point on" .)

I've seen this clue in the Sydney Morning Herald.
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