The first man's wife the night before (3)
I believe the answer is:
eve
This clue might be a double definition.
'the first man's wife' is the first definition.
The answer and definition can be both people as well as being singular nouns.
Maybe there's an association between them I don't understand?
'night before' is the second definition.
(eve can mean the night before something)
'the' is the link.
Can you help me to learn more?
(Other definitions for eve that I've seen before include "First lady from the night before" , "comes before Jan. 1st" , "The night before a festival" , "Day before (an event)" , "Threshold" .)