The most common and most likely answer to this crossword clue is the 10 letter word WINTERTIME
I've seen this crossword clue in The Daily Telegraph
W
I
N
T
E
R
T
I
M
E
More clues leading to the result WINTERTIME
Buddy explains!
The straight part
We know that "when it gets cold" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case when it gets cold = wintertime.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 WINTERTIME mean?
WINTERTIME noun- The season of winter, between autumn and spring