The most common and most likely answer to this crossword clue is the 7 plus 3 plus 3 plus 4 letter word BLOWING HOT AND COLD
I've seen this crossword clue in The Times
B
L
O
W
I
N
G
H
O
T
A
N
D
C
O
L
D
Buddy explains!
The straight part
We know that "Proving inconsistent/like sirocco and mistral" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case proving inconsistent/like sirocco and mistral = blowing hot and cold.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.