The most common and most likely answer to this crossword clue is the 4 letter word JUTE
I've seen this crossword clue in The Times
J
U
T
E
More clues leading to the result JUTE
- Project with European material
- Early settler’s source of fibre?
- Rough stuff from invader
- Project Fear's secondary element for unwelcome arrival in Britain?
- Protrude over centre of green fibrous plant
- Project close to failure: sacking may come from it
- Fibre supplying 19 across with energy
- Old British settler needed for 20?
- Stick out, bearing fibre
- It’s grown by old people mostly
Buddy explains!

The straight part
We know that "Rough stuff/invader" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rough stuff/invader = jute.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does JUTE mean?
JUTE noun- The coarse, strong fiber of the East Indian plants, Corchorus olitorius and Corchorus capsularis, used to make mats, paper, gunny cloth etc.
- The plants from which this fibre is obtained.