Heath shrub (5)
I believe the answer is:
gorse
'heath shrub' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for gorse that I've seen before include "Prickly moorland plant" , "Spiny evergreen shrub" , "Spiky shrub" , "Moorland shrub" , "Spiny yellow-flowered shrub" .)