The most common and most likely answer to this crossword clue is the 15 letter word FAHRENHEITSCALE
F
A
H
R
E
N
H
E
I
T
S
C
A
L
E
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.