Cut back coarse weed (4)
I believe the answer is:
dock
This might be a double definition.
'cut back' is the first definition.
(thesaurus)
'coarse weed' is the second definition.
'dock' can be an answer for 'weed' (type of weed). I am not sure about the 'coarse' bit.
Can you help me to learn more?
(Other definitions for dock that I've seen before include "Court enclosure; weed" , "Type of broad-leaved weed" , "Where the accused stands in court" , "Cut < leaf" , "Quay" .)