The most common and most likely answer to this crossword clue is the 6 plus 3 letter word GOLDEN AGE
I've seen this crossword clue in Financial Times
G
O
L
D
E
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A
G
E
More clues leading to the result GOLDEN AGE
- Best time is past to crack joke: start of evening
- . . . . or possibly a genie missing one happy time in the past?
- Joke about bygone English period before everything went to pot
- Engage organisation, get used to peace and prosperity
- Horse in endless action after record back in time of greatest achievement
Buddy explains!
The straight part
We know that "happy time in the past" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case happy time in the past = golden age.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.