The most common and most likely answer to this crossword clue is the 9 letter word UNDERSELL
I've seen this crossword clue in The Daily Telegraph
U
N
D
E
R
S
E
L
L
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 UNDERSELL mean?
UNDERSELL verb- To sell goods for a lower price than a competitor.
- To sell something for less than its value.
- To put forward an idea, or to market a new product, with insufficient enthusiasm.