The most common and most likely answer to this crossword clue is the 4 letter word ECRU
I've seen this crossword clue in The Guardian
E
C
R
U
More clues leading to the result ECRU
- Light colour of old city church to the west
- Pie crust somewhat greyish
- Light brown, as shown by the crumpet
- Off-white in spring returning? Not so
- Shade found in English vineyard
- Shade in colour certainly retro
- For commentator, top-class rowers showing natural colour
- Light brown part of pie crust
- Grey colour cell shows up
- Off-white linen carried by recruits
Buddy explains!

The straight part
We know that "linen that’s unbleached" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case linen that’s unbleached = ecru.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 ECRU mean?
ECRU noun- A beige colour.
- Of a beige colour.