The girl's in a depression, being a fan (8)
I believe the answer is:
adherent
'a fan' is the definition.
(I've seen this before)
'the girl's in a depression' is the wordplay.
'the girl's' becomes 'her' (belonging to a girl).
'in' means one lot of letters goes inside another.
'depression' becomes 'dent' (dent is a kind of depression).
'a'+'dent'='adent'
'her' going into 'adent' is 'ADHERENT'.
'being' is the link.
(Other definitions for adherent that I've seen before include "Person supporting" , "Freak" , "Disciple, follower" , "Staunch follower" , "One believes in and helps spread the doctrine of another" .)