Heather - a girl's name (5)
I believe the answer is:
erica
I believe this clue is a triple definition!
'heather' is the first definition.
(the plant genus Erica includes heather plants)
'a girl's' is the second definition.
(I've seen this before)
'name' is the third definition.
(Other definitions for erica that I've seen before include "Plant genus of garden heather" , "Heath genus; girl's name" , "Heather, for instance" , "ling" , "I care (anag) - plant - girl" .)