Plant of heath genus (5)
I believe the answer is:
'plant of heath genus' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for erica that I've seen before include "I care (anag) - plant - girl" , "Plant of the heath genus" , "Girl - heather" , "Moorland plant, girl's name" , "Girl's name - I care (anag)" .)