Heather is a woman (5)
I believe the answer is:
erica
This clue is a double definition.
'heather' is the first definition.
(the plant genus Erica includes heather plants)
'a woman' is the second definition.
'is' acts as a link.
(Other definitions for erica that I've seen before include "Plant genus of garden heather" , "Shrubs" , "I care (anag) - plant - girl" , "Girl's name - I care (anag)" , "Heather's Latin name?" .)