Clue: A noblewoman's unexceptional, if new, descendant (7)
Answer: BARONNE
Explanation: A noblewoman's unexceptional, if new, descendant (7)
BAR NONE ('unexceptional', in the sense of without exception) with the first N shuffled along a letter ('if new, descendant' in a down light). BARONNE, from the French, is a variant on baroness.