The most common and most likely answer to this crossword clue is the 9 letter word XEROPHYTE
I've seen this crossword clue in The Times
X
E
R
O
P
H
Y
T
E
Buddy explains!

The straight part
We know that "desert plant, say/to hype" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case desert plant, say/to hype = xerophyte.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 XEROPHYTE mean?
XEROPHYTE noun- Any plant suited for life in a habitat where water is scarce, such as in a desert or chaparral. Such plants may be succulent, have small or reduced leaves, or spines.
- A desert plant