The most common and most likely answer to this crossword clue is the 11 letter word NONDESCRIPT
I've seen this crossword clue in The Sunday Telegraph
N
O
N
D
E
S
C
R
I
P
T
More clues leading to the result NONDESCRIPT
- Intends crop to be processed as vanilla
- Donne in translation – writing becomes dull?
- Drama with end ruined by writing that’s undistinguished
- Undifferentiated network point plugged with new lines
- Unremarkable version of second print
- Second print-out is lacking in character
- Princes don’t turn out undistinguished
- Drama with end ruined by writing that's undistinguished
Buddy explains!

The straight part
We know that "Unremarkable" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unremarkable = nondescript.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 NONDESCRIPT mean?
NONDESCRIPT noun- A species or other type of creature that has not been previously described or identified.
- An undistinguished, unexceptional person or thing.
- An unmarked police car.
- Not described (in the academic literature).
- Without distinguishing qualities or characteristics.