The most common and most likely answer to this crossword clue is the 4 plus 5 plus 6 letter word WIND CHILL FACTOR
I've seen this crossword clue in The Daily Telegraph
W
I
N
D
C
H
I
L
L
F
A
C
T
O
R
More clues leading to the result WIND CHILL FACTOR
Buddy explains!

The straight part
We know that "indication of cold" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case indication of cold = wind chill factor.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.