To many a man, a precocious girl (5)
I believe the answer is:
madam
'a precocious girl' is the definition.
(I've seen this before)
'to many a man' is the wordplay.
'to many' becomes 'm'.
'a man' becomes 'adam' (Adam is an example).
'm'+'adam'='MADAM'
(Other definitions for madam that I've seen before include "Woman with status - girl with bad manners" , "Courteous form of address to a woman" , "Formal address to a woman - precocious little girl" , "Palindrome used in speaking politely to a woman" , "What you would call a female customer (or a spoiled girl!)" .)