In Ireland, a girl to love (4)
I believe the answer is:
mayo
'in ireland' is the definition.
(I know that Mayo is a county of Ireland)
'a girl to love' is the wordplay.
'a girl' becomes 'may' ().
'to love' becomes 'o' (love means zero in tennis).
'may'+'o'='MAYO'
(Other definitions for mayo that I've seen before include "Saucy thing" , "Salad dressing (abbr)" , "You'll find it in the Emerald Isle" , "part of Ireland" , "Eg, Braeburn or Cox" .)