The most common and most likely answer to this crossword clue is the 5 plus 7 letter word GRASS WIDOWER
I've seen this crossword clue in Independent
G
R
A
S
S
W
I
D
O
W
E
R
Buddy explains!
The straight part
We know that "his wife’s away" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case his wife’s away = grass widower.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.