Opposite of a day trip? (9)
I believe the answer is:
'opposite of a day trip?' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'opposite of a day trip?' is the wordplay.
'opposite of a day' becomes 'night' ('night' is the opposite to 'day').
'trip?' becomes 'fall' (trip can mean to fall over).
Can you help me to learn more?
(Other definitions for nightfall that I've seen before include "when visibility reduces" , "start of the dark time" , "End of day" , "Evening" , "when evenings draw in" .)