The most common and most likely answer to this crossword clue is the 10 letter word ISOTHERMAL
I've seen this crossword clue in The Guardian
I
S
O
T
H
E
R
M
A
L
More clues leading to the result ISOTHERMAL
- Earl in terrible hailstorm maintaining a temperature
- Bad storm and hail round east with temperature remaining constant
- Not changing temps — one’s female, but ____ ? Almost!
- Hailstorm breaks out around the east – it’s to do with temperature
- Hearst limo engineered to keep at constant temperature
- Hailstorm breaks out around East — it’s to do with temperature
Buddy explains!

The straight part
We know that "with temperature remaining constant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case with temperature remaining constant = isothermal.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 ISOTHERMAL mean?
ISOTHERMAL noun- An isotherm
- Of or pertaining to a process that takes place at constant temperature
- Of or pertaining to an isotherm