Leading lady here hosts love-in (7)
I believe the answer is:
heroine
'leading lady' is the definition.
(I've seen this in another clue)
'here hosts love-in' is the wordplay.
'hosts' indicates putting letters inside (inserted letters are welcomed or hosted).
'love' becomes 'o' (love means zero in tennis).
'o'+'in'='oin'
'here' placed around 'oin' is 'HEROINE'.
(Other definitions for heroine that I've seen before include "Brave woman" , "Chief female character in a book" , "Brave female" , "Leading lady" , "The main good female character in a work of fiction" .)