The most common and most likely answer to this crossword clue is the 10 letter word MIDDLEBROW
M
I
D
D
L
E
B
R
O
W
Buddy explains!

The straight part
We know that "not unduly demanding" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case not unduly demanding = middlebrow.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 MIDDLEBROW mean?
MIDDLEBROW noun- A person or thing that is neither highbrow nor lowbrow, but in between.
- Neither highbrow or lowbrow, but somewhere in between.