The most common and most likely answer to this crossword clue is the 7 letter word SUBZERO
I've seen this crossword clue in The Guardian
S
U
B
Z
E
R
O
More clues leading to the result SUBZERO
- Very cold press employee introducing cipher
- Very low temperature press employee’s Cockney idol reported
- Very cool reserves star at West Ham, we hear
- Frosty, definitively negative
- Negative rehash of Suez, involving British soldiers in retreat
- Last letter required to fill old puzzle, flipping bitter!
- Negative information about free membership to club?
- Freezing cold for unknown character among obscure characters in a storm
- Exceptionally cold and definitively negative
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 SUBZERO mean?
SUBZERO adjective- Less than zero, most commonly used to refer to temperature.