Sharpen up so he can carry on (4)
I believe the answer is:
hone
This could be a double definition.
'sharpen up' is the first definition.
(I've seen this in another clue)
'he can carry on' is the second definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'so' is the link.
Can you help me to learn more?
(Other definitions for hone that I've seen before include "Sharpen tool on stone" , "Strop" , "Polish" , "Sharpen (a blade)" , "Smooth stone" .)