Precocious girl (5)
I believe the answer is:
madam
'precocious girl' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for madam that I've seen before include "Palindrome used in speaking politely to a woman" , "Titled lady" , "Woman running a brothel" , "'Call Me ---' (I. Berlin)" , "pompous young lady?" .)