The most common and most likely answer to this crossword clue is the 6 letter word WELKIN
W
E
L
K
I
N
Buddy explains!
The straight part
We know that "Heavens" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case heavens = welkin.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 WELKIN mean?
WELKIN noun- The sky, the region of clouds; the upper air; aether; the heavens.