Girl in part of Lorraine's territory (5)
I believe the answer is:
nancy
'girl in part of lorraine's territory' is the definition.
'Nancy' can be an answer for 'girl'. I'm not sure about the 'in part of lorraine's territory' bit.
'girl in part of lorraine's' is the wordplay.
'girl' becomes 'Nan' (short for Nancy or Ann).
'in part of lorraine' becomes 'cy' (I can't justify this - if you can you should give a lot more credence to this answer).
'nan'+'cy'='NANCY'
Can you help me to learn more?
(Other definitions for nancy that I've seen before include "No Man" , "Birthplace of Edmond de Goncourt" , "Girl; French city" , "Note this French city" , "Bill Sikes's girl (Dickens)" .)