The most common and most likely answer to this crossword clue is the 10 letter word MONOTONOUS
I've seen this crossword clue in Independent
M
O
N
O
T
O
N
O
U
S
More clues leading to the result MONOTONOUS
Buddy explains!

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 MONOTONOUS mean?
MONOTONOUS adjective- Having an unvarying tone or pitch.
- Tedious, repetitious or lacking in variety.