Fail to be a turncoat, we hear? It’s intrusive (9)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
knotgrass
'fail' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for knotgrass that I've seen before include "Weed" , "plant" .)