First Lady not completely fair (3)
I believe the answer is:
eve
'first lady' is the definition.
(first woman in the Bible)
'not completely fair' is the wordplay.
'not completely' means to remove the last letter.
'fair' becomes 'even' (I've seen this before).
'even' with its final letter taken off is 'EVE'.
(Other definitions for eve that I've seen before include "Adam's wife" , "The night before a festival" , "First mate" , "Adam's partner" , "Adam & - -" .)