A keyhole affair (5)
I believe the answer is:
event
This might be a double definition.
'a keyhole' is the first definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'affair' is the second definition.
(I've seen this before)
Can you help me to learn more?
(Other definitions for event that I've seen before include "Occurence, occasion" , "Something happening" , "Planned public or social occasion" , "Occurence, happening" , "Result; incident" .)