Herb's girl (8)
I believe the answer is:
rosemary
This clue is a double definition.
'herb's' is the first definition.
(rosemary is a kind of herb)
'girl' is the second definition.
(Other definitions for rosemary that I've seen before include "-'s Baby, Roman Polanski film" , "Helps one to remember" , "One or two girls" , "Grey-green herb" , "Fragrant evergreen shrub and herb" .)