Email hacked by a girl (6)
I believe the answer is:
amelia
'girl' is the definition.
'email hacked by a' is the wordplay.
'hacked' is an anagram indicator (I've seen 'hacking' mean this).
'by' says to put letters next to each other.
'email' with letters rearranged gives 'ameli'.
'ameli'+'a'='AMELIA'
(Other definitions for amelia that I've seen before include "famous pilot" , "Legless condition" , "Fielding novel" , "Fielding heroine" , "I, a male (anag) - a woman" .)