There's a change in this girl (6)
I believe the answer is:
esther
'girl' is the definition.
'there's a change' is the wordplay.
'a change' indicates an anagram.
'theres' anagrammed gives 'ESTHER'.
'in this' acts as a link.
(Other definitions for esther that I've seen before include "Old Testament book that tells of a beautiful Jewess" , "Oratorio by Handel; girl's name" , "There's a biblical girl" , "Old Testament book telling of a beautiful Jewess" , "OT heroine" .)