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 they can define each other.
'look sharp' is the second definition.
The answer and definition can be both human attributes as well as being singular nouns.
Perhaps they are linked in a way 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" .)