County girl with a baby at last (6)
I believe the answer is:
galway
'county' is the definition.
(county of Ireland)
'girl with a baby at last' is the wordplay.
'girl' becomes 'gal' ().
'with' becomes 'w' (abbreviation).
'at last' suggests the final letters.
The final letter of 'baby' is 'y'.
'gal'+'w'+'a'+'y'='GALWAY'
(Other definitions for galway that I've seen before include "Irish city" , "W. Irish town, county, bay" , "County of W. Ireland" , "part of Ireland" , "flautist" .)