First lady gets new uniform (4)
I believe the answer is:
even
'uniform' is the definition.
(thesaurus)
'first lady gets new' is the wordplay.
'first lady' becomes 'eve' (I've seen this before).
'gets' means one lot of letters go next to another.
'new' becomes 'n'.
'eve'+'n'='EVEN'
(Other definitions for even that I've seen before include "Tied" , "That's not odd" , "Not bumpy" , "Flush" , "Like 2,4,6, ..." .)