Just the first lady and Biden, finally (4)
I believe the answer is:
even
'just' is the definition.
(thesaurus)
'the first lady and biden finally' is the wordplay.
'the first lady' becomes 'eve' (first woman in the Bible).
'and' says to put letters next to each other.
'finally' says to take the final letters.
The last letter of 'biden' is 'n'.
'eve'+'n'='EVEN'
(Other definitions for even that I've seen before include "Late in the day" , "Yet; smooth" , "Stable" , "Steady or smooth" , "without a rise?" .)