Large fern (7)
I believe the answer is:
bracken
'large fern' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bracken that I've seen before include "Type of fern" , "A mass of wild ferns" , "Coarse ferns" , "Common fern" , "Coarse moorland fern" .)