The most common and most likely answer to this crossword clue is the 5 plus 5 letter word DEMOB HAPPY
I've seen this crossword clue in The Guardian
D
E
M
O
B
H
A
P
P
Y
Buddy explains!
The straight part
We know that "Anticipating release" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case anticipating release = demob happy.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 DEMOB HAPPY mean?
DEMOB HAPPY adjective- Relieved and exhilarated by imminent release from a time-serving burden.