In which to look sharp (5)
I believe the answer is:
focus
This might be a double definition.
'in which' is the first definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'look sharp' is the second definition.
The definition and answer can be both human attributes as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'to' is the link.
Can you help me to learn more?
(Other definitions for focus that I've seen before include "Concentrate - type of group" , "Adjust (camera lens)" , "Centre of concentration" , "Central point" , "Concentrate, zero in" .)