A girl not entirely repellent (5)
I believe the answer is:
ellen
'a girl' is the definition.
'not entirely repellent' is the wordplay.
'not entirely' indicates a hidden word.
'ELLEN' is hidden in the letters of 'repellent'.
(Other definitions for ellen that I've seen before include "Girl" , "Woman" , "Girl's name" , "Dame - - Macarthur (naut.)" , "MacArthur, round-the-world yachtswoman" .)