The most common and most likely answer to this crossword clue is the 3 plus 4 plus 4 letter word QUE SERA SERA
I've seen this crossword clue in The Times
Q
U
E
S
E
R
A
S
E
R
A
More clues leading to the result QUE SERA SERA
Buddy explains!
The straight part
We know that "An air of resignation?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case an air of resignation? = que sera sera.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.